diff --git a/README.md b/README.md
index af74e1f5..b5449dd4 100644
--- a/README.md
+++ b/README.md
@@ -15,17 +15,21 @@ ph-css and ph-csscompress-maven-plugin are both licensed under the **Apache 2.0
 ## News and noteworthy
 
   * v5.0.2 - 2016-xx-yy
-      * Made tab size configurable (issue #29)
-      * Improved media expressions (issue #30)
+    * Made tab size configurable (issue #29)
+    * Improved media expressions (issue #30)
+    * Allowing to disable consistency checks in class `CSSValue`
+    * Made CSS interpretation warnings customizable with class `ICSSInterpretErrorHandler` (issue #33)
   * v5.0.1 - 2016-08-17
     * Using "modern java template" for JavaCC parser - results in quicker execution
     * Enhancement issue #27
-    * Intergated `ph-csscompress-maven-plugin` into this repository
+    * Integrated `ph-csscompress-maven-plugin` into this repository
     * Bug fix wrong OutputStream (issue #28) 
   * v5.0.0 - 2016-06-12
     * Using JDK8 as the basis
     * removed explicit grammar for CSS 2.1 (issue #20)
     * Added browser compliant error handler
+  * v4.1.6 - 2016-xx-yy
+    * Made CSS interpretation warnings customizable with class `ICSSInterpretErrorHandler` (issue #33)
   * v4.1.5 - 2016-09-16
     * Improved media expressions (issue #30)
     * Integrated ph-csscompress-maven-plugin into this project (compatibility to 5.x)
diff --git a/ph-css/src/main/java/com/helger/css/ECSSVersion.java b/ph-css/src/main/java/com/helger/css/ECSSVersion.java
index bf57d4e8..067e74d8 100644
--- a/ph-css/src/main/java/com/helger/css/ECSSVersion.java
+++ b/ph-css/src/main/java/com/helger/css/ECSSVersion.java
@@ -30,8 +30,10 @@
 public enum ECSSVersion implements IHasVersion
 {
   // Sort fields according to the version!
-  @DevelopersNote ("No CSS parser is available for 1.0!") CSS10(new Version (1, 0)),
-  @DevelopersNote ("Up to version 4.x of ph-css a special CSS 2.1 parser was available") CSS21(new Version (2, 1)),
+  @DevelopersNote ("No CSS parser is available for 1.0!")
+  CSS10(new Version (1, 0)),
+  @DevelopersNote ("Up to version 4.x of ph-css a special CSS 2.1 parser was available. Now it is the same as CSS 3.0")
+  CSS21(new Version (2, 1)),
   CSS30 (new Version (3, 0));
 
   /** Latest version is CSS 3.0 */
diff --git a/ph-css/src/main/java/com/helger/css/handler/CSSHandler.java b/ph-css/src/main/java/com/helger/css/handler/CSSHandler.java
index 6cad284b..eeefbc83 100644
--- a/ph-css/src/main/java/com/helger/css/handler/CSSHandler.java
+++ b/ph-css/src/main/java/com/helger/css/handler/CSSHandler.java
@@ -17,14 +17,19 @@
 package com.helger.css.handler;
 
 import javax.annotation.Nonnull;
+import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.Immutable;
 
 import com.helger.commons.ValueEnforcer;
 import com.helger.commons.annotation.PresentForCodeCoverage;
+import com.helger.commons.concurrent.SimpleReadWriteLock;
 import com.helger.css.ECSSVersion;
 import com.helger.css.decl.CSSDeclarationList;
 import com.helger.css.decl.CascadingStyleSheet;
 import com.helger.css.parser.CSSNode;
+import com.helger.css.reader.CSSReader;
+import com.helger.css.reader.errorhandler.ICSSInterpretErrorHandler;
+import com.helger.css.reader.errorhandler.LoggingCSSInterpretErrorHandler;
 
 /**
  * This class is the entry point for converting AST nodes from the parser to
@@ -35,6 +40,11 @@
 @Immutable
 public final class CSSHandler
 {
+  private static final SimpleReadWriteLock s_aRWLock = new SimpleReadWriteLock ();
+
+  @GuardedBy ("s_aRWLock")
+  private static ICSSInterpretErrorHandler s_aDefaultInterpretErrorHandler = new LoggingCSSInterpretErrorHandler ();
+
   @PresentForCodeCoverage
   private static final CSSHandler s_aInstance = new CSSHandler ();
 
@@ -51,15 +61,37 @@ private CSSHandler ()
    * @return Never <code>null</code>.
    */
   @Nonnull
+  @Deprecated
   public static CascadingStyleSheet readCascadingStyleSheetFromNode (@Nonnull final ECSSVersion eVersion,
                                                                      @Nonnull final CSSNode aNode)
+  {
+    return readCascadingStyleSheetFromNode (eVersion, aNode, CSSReader.getDefaultInterpretErrorHandler ());
+  }
+
+  /**
+   * Create a {@link CascadingStyleSheet} object from a parsed object.
+   *
+   * @param eVersion
+   *        The CSS version to use. May not be <code>null</code>.
+   * @param aNode
+   *        The parsed CSS object to read. May not be <code>null</code>.
+   * @param aErrorHandler
+   *        The error handler to be used. May not be <code>null</code>.
+   * @return Never <code>null</code>.
+   * @since 5.0.2
+   */
+  @Nonnull
+  public static CascadingStyleSheet readCascadingStyleSheetFromNode (@Nonnull final ECSSVersion eVersion,
+                                                                     @Nonnull final CSSNode aNode,
+                                                                     @Nonnull final ICSSInterpretErrorHandler aErrorHandler)
   {
     ValueEnforcer.notNull (eVersion, "Version");
     ValueEnforcer.notNull (aNode, "Node");
     if (!ECSSNodeType.ROOT.isNode (aNode, eVersion))
       throw new CSSHandlingException (aNode, "Passed node is not a root node!");
+    ValueEnforcer.notNull (aErrorHandler, "ErrorHandler");
 
-    return new CSSNodeToDomainObject (eVersion).createCascadingStyleSheetFromNode (aNode);
+    return new CSSNodeToDomainObject (eVersion, aErrorHandler).createCascadingStyleSheetFromNode (aNode);
   }
 
   /**
@@ -72,14 +104,36 @@ public static CascadingStyleSheet readCascadingStyleSheetFromNode (@Nonnull fina
    * @return Never <code>null</code>.
    */
   @Nonnull
+  @Deprecated
   public static CSSDeclarationList readDeclarationListFromNode (@Nonnull final ECSSVersion eVersion,
                                                                 @Nonnull final CSSNode aNode)
+  {
+    return readDeclarationListFromNode (eVersion, aNode, CSSReader.getDefaultInterpretErrorHandler ());
+  }
+
+  /**
+   * Create a {@link CSSDeclarationList} object from a parsed object.
+   *
+   * @param eVersion
+   *        The CSS version to use. May not be <code>null</code>.
+   * @param aNode
+   *        The parsed CSS object to read. May not be <code>null</code>.
+   * @param aErrorHandler
+   *        The error handler to be used. May not be <code>null</code>.
+   * @return Never <code>null</code>.
+   * @since 5.0.2
+   */
+  @Nonnull
+  public static CSSDeclarationList readDeclarationListFromNode (@Nonnull final ECSSVersion eVersion,
+                                                                @Nonnull final CSSNode aNode,
+                                                                @Nonnull final ICSSInterpretErrorHandler aErrorHandler)
   {
     ValueEnforcer.notNull (eVersion, "Version");
     ValueEnforcer.notNull (aNode, "Node");
     if (!ECSSNodeType.STYLEDECLARATIONLIST.isNode (aNode, eVersion))
       throw new CSSHandlingException (aNode, "Passed node is not a style declaration node!");
+    ValueEnforcer.notNull (aErrorHandler, "ErrorHandler");
 
-    return new CSSNodeToDomainObject (eVersion).createDeclarationListFromNode (aNode);
+    return new CSSNodeToDomainObject (eVersion, aErrorHandler).createDeclarationListFromNode (aNode);
   }
 }
diff --git a/ph-css/src/main/java/com/helger/css/handler/CSSNodeToDomainObject.java b/ph-css/src/main/java/com/helger/css/handler/CSSNodeToDomainObject.java
index c2783589..fdd1dcf9 100644
--- a/ph-css/src/main/java/com/helger/css/handler/CSSNodeToDomainObject.java
+++ b/ph-css/src/main/java/com/helger/css/handler/CSSNodeToDomainObject.java
@@ -22,9 +22,6 @@
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import com.helger.commons.ValueEnforcer;
 import com.helger.commons.annotation.Nonempty;
 import com.helger.commons.collection.ext.CommonsArrayList;
@@ -77,6 +74,7 @@
 import com.helger.css.media.ECSSMedium;
 import com.helger.css.parser.CSSNode;
 import com.helger.css.parser.CSSParseHelper;
+import com.helger.css.reader.errorhandler.ICSSInterpretErrorHandler;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 
@@ -89,19 +87,22 @@
 @NotThreadSafe
 final class CSSNodeToDomainObject
 {
-  private static final Logger s_aLogger = LoggerFactory.getLogger (CSSNodeToDomainObject.class);
-
   private final ECSSVersion m_eVersion;
+  private final ICSSInterpretErrorHandler m_aErrorHandler;
 
   /**
    * Constructor
    *
    * @param eVersion
    *        The CSS version to use. May not be <code>null</code>.
+   * @param aErrorHandler
+   *        Error handler to use. May not be <code>null</code>.
    */
-  public CSSNodeToDomainObject (@Nonnull final ECSSVersion eVersion)
+  public CSSNodeToDomainObject (@Nonnull final ECSSVersion eVersion,
+                                @Nonnull final ICSSInterpretErrorHandler aErrorHandler)
   {
     m_eVersion = ValueEnforcer.notNull (eVersion, "Version");
+    m_aErrorHandler = ValueEnforcer.notNull (aErrorHandler, "ErrorHandler");
   }
 
   private void _expectNodeType (@Nonnull final CSSNode aNode, @Nonnull final ECSSNodeType eExpected)
@@ -115,11 +116,11 @@ private void _expectNodeType (@Nonnull final CSSNode aNode, @Nonnull final ECSSN
                                              "'");
   }
 
-  private static void _throwUnexpectedChildrenCount (@Nonnull final CSSNode aNode, @Nonnull @Nonempty final String sMsg)
+  private void _throwUnexpectedChildrenCount (@Nonnull final CSSNode aNode, @Nonnull @Nonempty final String sMsg)
   {
-    s_aLogger.error (sMsg);
+    m_aErrorHandler.onCSSInterpretationError (sMsg);
     for (int i = 0; i < aNode.jjtGetNumChildren (); ++i)
-      s_aLogger.error ("  " + aNode.jjtGetChild (i));
+      m_aErrorHandler.onCSSInterpretationError ("  " + aNode.jjtGetChild (i));
     throw new CSSHandlingException (aNode, sMsg);
   }
 
@@ -171,11 +172,12 @@ private CSSImportRule _createImportRule (@Nonnull final CSSNode aNode)
         ++nCurrentIndex;
       }
       else
-        s_aLogger.error ("Expected an MEDIALIST node but got " + ECSSNodeType.getNodeName (aMediaListNode, m_eVersion));
+        m_aErrorHandler.onCSSInterpretationError ("Expected an MEDIALIST node but got " +
+                                                  ECSSNodeType.getNodeName (aMediaListNode, m_eVersion));
     }
 
     if (nCurrentIndex < nChildCount)
-      s_aLogger.error ("Import statement has children which are unhandled.");
+      m_aErrorHandler.onCSSInterpretationError ("Import statement has children which are unhandled.");
     return ret;
   }
 
@@ -253,7 +255,7 @@ private ICSSSelectorMember _createSelectorMember (final CSSNode aNode)
       final String sText = aNode.getText ();
       final ECSSSelectorCombinator eCombinator = ECSSSelectorCombinator.getFromNameOrNull (sText);
       if (eCombinator == null)
-        s_aLogger.error ("Failed to parse CSS selector combinator '" + sText + "'");
+        m_aErrorHandler.onCSSInterpretationError ("Failed to parse CSS selector combinator '" + sText + "'");
       return eCombinator;
     }
 
@@ -309,7 +311,8 @@ private ICSSSelectorMember _createSelectorMember (final CSSNode aNode)
                                                aNode.toString ());
     }
 
-    s_aLogger.error ("Unsupported selector child: " + ECSSNodeType.getNodeName (aNode, m_eVersion));
+    m_aErrorHandler.onCSSInterpretationError ("Unsupported selector child: " +
+                                              ECSSNodeType.getNodeName (aNode, m_eVersion));
     return null;
   }
 
@@ -375,15 +378,15 @@ private CSSExpressionMemberMathProduct _createExpressionMathProduct (@Nonnull fi
                   final String sText = aChildChildNode.getText ();
                   final ECSSMathOperator eMathOp = ECSSMathOperator.getFromNameOrNull (sText);
                   if (eMathOp == null)
-                    s_aLogger.error ("Failed to parse math operator '" + sText + "'");
+                    m_aErrorHandler.onCSSInterpretationError ("Failed to parse math operator '" + sText + "'");
                   else
                     aNestedProduct.addMember (eMathOp);
                 }
                 else
-                  s_aLogger.error ("Unsupported child of " +
-                                   ECSSNodeType.getNodeName (aChildNode, m_eVersion) +
-                                   ": " +
-                                   ECSSNodeType.getNodeName (aChildChildNode, m_eVersion));
+                  m_aErrorHandler.onCSSInterpretationError ("Unsupported child of " +
+                                                            ECSSNodeType.getNodeName (aChildNode, m_eVersion) +
+                                                            ": " +
+                                                            ECSSNodeType.getNodeName (aChildChildNode, m_eVersion));
             }
             ret.addMember (new CSSExpressionMemberMathUnitProduct (aNestedProduct));
           }
@@ -394,15 +397,15 @@ private CSSExpressionMemberMathProduct _createExpressionMathProduct (@Nonnull fi
           final String sText = aChildNode.getText ();
           final ECSSMathOperator eMathOp = ECSSMathOperator.getFromNameOrNull (sText);
           if (eMathOp == null)
-            s_aLogger.error ("Failed to parse math product operator '" + sText + "'");
+            m_aErrorHandler.onCSSInterpretationError ("Failed to parse math product operator '" + sText + "'");
           else
             ret.addMember (eMathOp);
         }
         else
-          s_aLogger.error ("Unsupported child of " +
-                           ECSSNodeType.getNodeName (aNode, m_eVersion) +
-                           ": " +
-                           ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+          m_aErrorHandler.onCSSInterpretationError ("Unsupported child of " +
+                                                    ECSSNodeType.getNodeName (aNode, m_eVersion) +
+                                                    ": " +
+                                                    ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
 
     return ret;
@@ -470,15 +473,15 @@ private CSSExpressionMemberMath _createExpressionMathTerm (@Nonnull final CSSNod
           final String sText = aChildNode.getText ();
           final ECSSMathOperator eMathOp = ECSSMathOperator.getFromNameOrNull (sText);
           if (eMathOp == null)
-            s_aLogger.error ("Failed to parse math operator '" + sText + "'");
+            m_aErrorHandler.onCSSInterpretationError ("Failed to parse math operator '" + sText + "'");
           else
             ret.addMember (eMathOp);
         }
         else
-          s_aLogger.error ("Unsupported child of " +
-                           ECSSNodeType.getNodeName (aNode, m_eVersion) +
-                           ": " +
-                           ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+          m_aErrorHandler.onCSSInterpretationError ("Unsupported child of " +
+                                                    ECSSNodeType.getNodeName (aNode, m_eVersion) +
+                                                    ": " +
+                                                    ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
 
     return ret;
@@ -540,16 +543,16 @@ private CSSExpression _createExpression (@Nonnull final CSSNode aNode)
           final String sText = aChildNode.getText ();
           final ECSSExpressionOperator eOp = ECSSExpressionOperator.getFromNameOrNull (sText);
           if (eOp == null)
-            s_aLogger.error ("Failed to parse expression operator '" + sText + "'");
+            m_aErrorHandler.onCSSInterpretationError ("Failed to parse expression operator '" + sText + "'");
           else
             ret.addMember (eOp);
         }
         else
         {
-          s_aLogger.error ("Unsupported child of " +
-                           ECSSNodeType.getNodeName (aNode, m_eVersion) +
-                           ": " +
-                           ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+          m_aErrorHandler.onCSSInterpretationError ("Unsupported child of " +
+                                                    ECSSNodeType.getNodeName (aNode, m_eVersion) +
+                                                    ": " +
+                                                    ECSSNodeType.getNodeName (aChildNode, m_eVersion));
         }
     }
     return ret;
@@ -585,10 +588,10 @@ private CSSDeclaration _createDeclaration (@Nonnull final CSSNode aNode)
       if (ECSSNodeType.IMPORTANT.isNode (aChildNode, m_eVersion))
         bImportant = true;
       else
-        s_aLogger.error ("Expected an " +
-                         ECSSNodeType.IMPORTANT.getNodeName (m_eVersion) +
-                         " token but got a " +
-                         ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+        m_aErrorHandler.onCSSInterpretationError ("Expected an " +
+                                                  ECSSNodeType.IMPORTANT.getNodeName (m_eVersion) +
+                                                  " token but got a " +
+                                                  ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
 
     final CSSDeclaration ret = new CSSDeclaration (sProperty, aExpression, bImportant);
@@ -628,7 +631,7 @@ private CSSStyleRule _createStyleRule (@Nonnull final CSSNode aNode)
       if (ECSSNodeType.SELECTOR.isNode (aChildNode, m_eVersion))
       {
         if (!bSelectors)
-          s_aLogger.error ("Found a selector after a declaration!");
+          m_aErrorHandler.onCSSInterpretationError ("Found a selector after a declaration!");
 
         ret.addSelector (_createSelector (aChildNode));
       }
@@ -643,10 +646,10 @@ private CSSStyleRule _createStyleRule (@Nonnull final CSSNode aNode)
         }
         else
           if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-            s_aLogger.error ("Unsupported child of " +
-                             ECSSNodeType.getNodeName (aNode, m_eVersion) +
-                             ": " +
-                             ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+            m_aErrorHandler.onCSSInterpretationError ("Unsupported child of " +
+                                                      ECSSNodeType.getNodeName (aNode, m_eVersion) +
+                                                      ": " +
+                                                      ECSSNodeType.getNodeName (aChildNode, m_eVersion));
       }
     }
 
@@ -712,8 +715,8 @@ private CSSPageRule _createPageRule (@Nonnull final CSSNode aNode)
           }
           else
             if (!ECSSNodeType.isErrorNode (aBodyChildNode, m_eVersion))
-              s_aLogger.error ("Unsupported page rule body child: " +
-                               ECSSNodeType.getNodeName (aBodyChildNode, m_eVersion));
+              m_aErrorHandler.onCSSInterpretationError ("Unsupported page rule body child: " +
+                                                        ECSSNodeType.getNodeName (aBodyChildNode, m_eVersion));
       }
 
       return ret;
@@ -745,7 +748,8 @@ private CSSPageRule _createPageRule (@Nonnull final CSSNode aNode)
         }
         else
           if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-            s_aLogger.error ("Unsupported page rule child: " + ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+            m_aErrorHandler.onCSSInterpretationError ("Unsupported page rule child: " +
+                                                      ECSSNodeType.getNodeName (aChildNode, m_eVersion));
       }
       return ret;
     }
@@ -794,8 +798,8 @@ private CSSMediaRule _createMediaRule (@Nonnull final CSSNode aNode)
                       ret.addRule (_createSupportsRule (aChildNode));
                     else
                       if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-                        s_aLogger.error ("Unsupported media-rule child: " +
-                                         ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+                        m_aErrorHandler.onCSSInterpretationError ("Unsupported media-rule child: " +
+                                                                  ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
     return ret;
   }
@@ -809,7 +813,11 @@ private CSSMediaQuery _createMediaQuery (@Nonnull final CSSNode aNode)
       // CSS 2.1 compatibility
       final String sMedium = aNode.getText ();
       if (ECSSMedium.getFromNameOrNull (sMedium) == null)
-        s_aLogger.warn ("CSS " + m_eVersion.getVersionString () + " Media query uses unknown medium '" + sMedium + "'");
+        m_aErrorHandler.onCSSInterpretationWarning ("CSS " +
+                                                    m_eVersion.getVersionString () +
+                                                    " Media query uses unknown medium '" +
+                                                    sMedium +
+                                                    "'");
       final CSSMediaQuery ret = new CSSMediaQuery (EModifier.NONE, sMedium);
       ret.setSourceLocation (aNode.getSourceLocation ());
       return ret;
@@ -838,7 +846,7 @@ private CSSMediaQuery _createMediaQuery (@Nonnull final CSSNode aNode)
             if ("only".equalsIgnoreCase (sMediaModifier))
               eModifier = EModifier.ONLY;
             else
-              s_aLogger.error ("Unsupported media modifier '" + sMediaModifier + "' found!");
+              m_aErrorHandler.onCSSInterpretationError ("Unsupported media modifier '" + sMediaModifier + "' found!");
         }
         ++nStartIndex;
       }
@@ -853,11 +861,11 @@ private CSSMediaQuery _createMediaQuery (@Nonnull final CSSNode aNode)
       {
         sMedium = aNextChild.getText ();
         if (ECSSMedium.getFromNameOrNull (sMedium) == null)
-          s_aLogger.warn ("CSS " +
-                          m_eVersion.getVersionString () +
-                          " media query uses unknown medium '" +
-                          sMedium +
-                          "'");
+          m_aErrorHandler.onCSSInterpretationWarning ("CSS " +
+                                                      m_eVersion.getVersionString () +
+                                                      " media query uses unknown medium '" +
+                                                      sMedium +
+                                                      "'");
         ++nStartIndex;
       }
     }
@@ -871,7 +879,8 @@ private CSSMediaQuery _createMediaQuery (@Nonnull final CSSNode aNode)
         ret.addMediaExpression (_createMediaExpr (aChildNode));
       else
         if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-          s_aLogger.error ("Unsupported media query child: " + ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+          m_aErrorHandler.onCSSInterpretationError ("Unsupported media query child: " +
+                                                    ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
     return ret;
   }
@@ -890,7 +899,7 @@ private CSSMediaExpression _createMediaExpr (@Nonnull final CSSNode aNode)
                                        ECSSNodeType.getNodeName (aFeatureNode, m_eVersion));
     final String sFeature = aFeatureNode.getText ();
     if (ECSSMediaExpressionFeature.getFromNameOrNull (sFeature) == null)
-      s_aLogger.warn ("Media expression uses unknown feature '" + sFeature + "'");
+      m_aErrorHandler.onCSSInterpretationWarning ("Media expression uses unknown feature '" + sFeature + "'");
 
     CSSMediaExpression ret;
     if (nChildCount == 1)
@@ -925,7 +934,8 @@ private CSSFontFaceRule _createFontFaceRule (@Nonnull final CSSNode aNode)
       }
       else
         if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-          s_aLogger.error ("Unsupported font-face rule child: " + ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+          m_aErrorHandler.onCSSInterpretationError ("Unsupported font-face rule child: " +
+                                                    ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
     return ret;
   }
@@ -981,7 +991,8 @@ private CSSKeyframesRule _createKeyframesRule (@Nonnull final CSSNode aNode)
         }
         else
           if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-            s_aLogger.error ("Unsupported keyframes rule child: " + ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+            m_aErrorHandler.onCSSInterpretationError ("Unsupported keyframes rule child: " +
+                                                      ECSSNodeType.getNodeName (aChildNode, m_eVersion));
 
       ++nIndex;
     }
@@ -1008,7 +1019,8 @@ private CSSViewportRule _createViewportRule (@Nonnull final CSSNode aNode)
       }
       else
         if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-          s_aLogger.error ("Unsupported viewport rule child: " + ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+          m_aErrorHandler.onCSSInterpretationError ("Unsupported viewport rule child: " +
+                                                    ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
     return ret;
   }
@@ -1095,13 +1107,14 @@ private ICSSSupportsConditionMember _createSupportsConditionMemberRecursive (@No
         return ret;
       }
 
-      s_aLogger.error ("Unsupported supportsConditionInParents child: " +
-                       ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+      m_aErrorHandler.onCSSInterpretationError ("Unsupported supportsConditionInParents child: " +
+                                                ECSSNodeType.getNodeName (aChildNode, m_eVersion));
       return null;
     }
 
     if (!ECSSNodeType.isErrorNode (aNode, m_eVersion))
-      s_aLogger.error ("Unsupported supports-condition child: " + ECSSNodeType.getNodeName (aNode, m_eVersion));
+      m_aErrorHandler.onCSSInterpretationError ("Unsupported supports-condition child: " +
+                                                ECSSNodeType.getNodeName (aNode, m_eVersion));
 
     return null;
   }
@@ -1150,8 +1163,8 @@ private CSSSupportsRule _createSupportsRule (@Nonnull final CSSNode aNode)
                       ret.addRule (_createSupportsRule (aChildNode));
                     else
                       if (!ECSSNodeType.isErrorNode (aChildNode, m_eVersion))
-                        s_aLogger.error ("Unsupported supports-rule child: " +
-                                         ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+                        m_aErrorHandler.onCSSInterpretationError ("Unsupported supports-rule child: " +
+                                                                  ECSSNodeType.getNodeName (aChildNode, m_eVersion));
     }
     return ret;
   }
@@ -1233,10 +1246,11 @@ public CascadingStyleSheet createCascadingStyleSheetFromNode (@Nonnull final CSS
                             ret.addRule (_createUnknownRule (aChildNode));
                           }
                           else
-                            s_aLogger.error ("Unsupported child of " +
-                                             ECSSNodeType.getNodeName (aNode, m_eVersion) +
-                                             ": " +
-                                             ECSSNodeType.getNodeName (aChildNode, m_eVersion));
+                            m_aErrorHandler.onCSSInterpretationError ("Unsupported child of " +
+                                                                      ECSSNodeType.getNodeName (aNode, m_eVersion) +
+                                                                      ": " +
+                                                                      ECSSNodeType.getNodeName (aChildNode,
+                                                                                                m_eVersion));
     }
     return ret;
   }
diff --git a/ph-css/src/main/java/com/helger/css/parser/AbstractParserCSS.java b/ph-css/src/main/java/com/helger/css/parser/AbstractParserCSS.java
index 2425dd7a..788796d2 100644
--- a/ph-css/src/main/java/com/helger/css/parser/AbstractParserCSS.java
+++ b/ph-css/src/main/java/com/helger/css/parser/AbstractParserCSS.java
@@ -37,35 +37,57 @@ public abstract class AbstractParserCSS
   protected ICSSParseErrorHandler m_aCustomErrorHandler;
   protected boolean m_bBrowserCompliantMode = false;
 
+  /**
+   * Set a custom error handler to use.
+   *
+   * @param aCustomErrorHandler
+   *        The custom error handler to use. May be <code>null</code>.
+   */
   public final void setCustomErrorHandler (@Nullable final ICSSParseErrorHandler aCustomErrorHandler)
   {
     m_aCustomErrorHandler = aCustomErrorHandler;
   }
 
+  /**
+   * @return The custom error handler to be used for this parser. May be
+   *         <code>null</code>.
+   */
   @Nullable
   public final ICSSParseErrorHandler getCustomErrorHandler ()
   {
     return m_aCustomErrorHandler;
   }
 
+  /**
+   * Enable or disable browser compliant mode.
+   *
+   * @param bBrowserCompliantMode
+   *        <code>true</code> to enable browser compliant mode,
+   *        <code>false</code> to disable it.
+   */
   public final void setBrowserCompliantMode (final boolean bBrowserCompliantMode)
   {
     m_bBrowserCompliantMode = bBrowserCompliantMode;
   }
 
+  /**
+   * @return <code>true</code> if browser compliant mode is active,
+   *         <code>false</code> if not. By default browser compliant mode is
+   *         disabled.
+   */
   public final boolean isBrowserCompliantMode ()
   {
     return m_bBrowserCompliantMode;
   }
 
   // Used when NODE_SCOPE_HOOK is true - for debugging only
-  // Package scope to avoid warning when NODE_SCOPE_HOOK is false
   public void jjtreeOpenNodeScope (final Node aNode)
   {
     if (s_aLogger.isDebugEnabled ())
       s_aLogger.debug ("Opening scope for " + aNode.toString ());
   }
 
+  // Used when NODE_SCOPE_HOOK is true - for debugging only
   public void jjtreeCloseNodeScope (final Node aNode)
   {
     if (s_aLogger.isDebugEnabled ())
diff --git a/ph-css/src/main/java/com/helger/css/propertyvalue/CSSValue.java b/ph-css/src/main/java/com/helger/css/propertyvalue/CSSValue.java
index b63e02cb..1bf16e04 100644
--- a/ph-css/src/main/java/com/helger/css/propertyvalue/CSSValue.java
+++ b/ph-css/src/main/java/com/helger/css/propertyvalue/CSSValue.java
@@ -47,7 +47,35 @@
 @NotThreadSafe
 public class CSSValue implements ICSSValue
 {
+  public static final boolean DEFAULT_CONSISTENCY_CHECKS_ENABLED = true;
+
   private static final Logger s_aLogger = LoggerFactory.getLogger (CSSValue.class);
+  private static boolean s_bConsistencyChecksEnabled = DEFAULT_CONSISTENCY_CHECKS_ENABLED;
+
+  /**
+   * @return <code>true</code> if consistency checks are enabled (by default),
+   *         <code>false</code> if not.
+   * @since 5.0.2
+   */
+  public static boolean areConsistencyChecksEnabled ()
+  {
+    return s_bConsistencyChecksEnabled;
+  }
+
+  /**
+   * Enable or disable consistency checks. By default the consistency checks are
+   * enabled (for backwards compatibility) but if performance is a real matter,
+   * you may want to disable them globally.
+   * 
+   * @param bEnabled
+   *        <code>true</code> to enable them, <code>false</code> to disable
+   *        them.
+   * @since 5.0.2
+   */
+  public static void setConsistencyChecksEnabled (final boolean bEnabled)
+  {
+    s_bConsistencyChecksEnabled = bEnabled;
+  }
 
   private ICSSProperty m_aProperty;
   private String m_sValue;
@@ -142,18 +170,22 @@ public String getValue ()
   public CSSValue setValue (@Nonnull final String sValue)
   {
     ValueEnforcer.notNull (sValue, "Value");
-    if (!m_aProperty.isValidValue (sValue))
-      s_aLogger.warn ("CSS: the value '" +
-                      sValue +
-                      "' is not valid for property '" +
-                      m_aProperty.getPropertyName () +
-                      "'");
-    if (sValue.contains (CCSS.IMPORTANT_SUFFIX))
-      s_aLogger.warn ("CSS: the value '" +
-                      sValue +
-                      "' should not contain the '" +
-                      CCSS.IMPORTANT_SUFFIX +
-                      "' string! Use 'setImportant' method instead.");
+
+    if (areConsistencyChecksEnabled ())
+    {
+      if (!m_aProperty.isValidValue (sValue))
+        s_aLogger.warn ("CSS: the value '" +
+                        sValue +
+                        "' is not valid for property '" +
+                        m_aProperty.getPropertyName () +
+                        "'");
+      if (sValue.contains (CCSS.IMPORTANT_SUFFIX))
+        s_aLogger.warn ("CSS: the value '" +
+                        sValue +
+                        "' should not contain the '" +
+                        CCSS.IMPORTANT_SUFFIX +
+                        "' string! Use 'setImportant' method instead.");
+    }
     m_sValue = sValue.trim ();
     return this;
   }
diff --git a/ph-css/src/main/java/com/helger/css/reader/CSSReader.java b/ph-css/src/main/java/com/helger/css/reader/CSSReader.java
index 3511c048..0fe0820e 100644
--- a/ph-css/src/main/java/com/helger/css/reader/CSSReader.java
+++ b/ph-css/src/main/java/com/helger/css/reader/CSSReader.java
@@ -63,7 +63,9 @@
 import com.helger.css.parser.ParserCSS30TokenManager;
 import com.helger.css.parser.ParserCSSCharsetDetector;
 import com.helger.css.parser.ParserCSSCharsetDetectorTokenManager;
+import com.helger.css.reader.errorhandler.ICSSInterpretErrorHandler;
 import com.helger.css.reader.errorhandler.ICSSParseErrorHandler;
+import com.helger.css.reader.errorhandler.LoggingCSSInterpretErrorHandler;
 import com.helger.css.reader.errorhandler.ThrowingCSSParseErrorHandler;
 
 /**
@@ -88,6 +90,9 @@ public final class CSSReader
   @GuardedBy ("s_aRWLock")
   private static ICSSParseExceptionCallback s_aDefaultParseExceptionHandler = new LoggingCSSParseExceptionCallback ();
 
+  @GuardedBy ("s_aRWLock")
+  private static ICSSInterpretErrorHandler s_aDefaultInterpretErrorHandler = new LoggingCSSInterpretErrorHandler ();
+
   @PresentForCodeCoverage
   private static final CSSReader s_aInstance = new CSSReader ();
 
@@ -144,6 +149,32 @@ public static void setDefaultParseExceptionHandler (@Nonnull final ICSSParseExce
     s_aRWLock.writeLocked ( () -> s_aDefaultParseExceptionHandler = aDefaultParseExceptionHandler);
   }
 
+  /**
+   * @return The default interpret error handler to handle interpretation errors
+   *         in successfully parsed CSS. Never <code>null</code>.
+   * @since 5.0.2
+   */
+  @Nonnull
+  public static ICSSInterpretErrorHandler getDefaultInterpretErrorHandler ()
+  {
+    return s_aRWLock.readLocked ( () -> s_aDefaultInterpretErrorHandler);
+  }
+
+  /**
+   * Set the default interpret error handler to handle interpretation errors in
+   * successfully parsed CSS.
+   *
+   * @param aDefaultErrorHandler
+   *        The default error handler to be used. May not be <code>null</code>.
+   * @since 5.0.2
+   */
+  public static void setDefaultInterpretErrorHandler (@Nonnull final ICSSInterpretErrorHandler aDefaultErrorHandler)
+  {
+    ValueEnforcer.notNull (aDefaultErrorHandler, "DefaultErrorHandler");
+
+    s_aRWLock.writeLocked ( () -> s_aDefaultInterpretErrorHandler = aDefaultErrorHandler);
+  }
+
   /**
    * Main reading of the CSS
    *
@@ -1112,29 +1143,34 @@ public static CascadingStyleSheet readFromStream (@Nonnull final IHasInputStream
       aCharStream.setTabSize (aSettings.getTabSize ());
 
       // Use the default CSS parse error handler if none is provided
-      ICSSParseErrorHandler aRealErrorHandler = aSettings.getCustomErrorHandler ();
-      if (aRealErrorHandler == null)
-        aRealErrorHandler = getDefaultParseErrorHandler ();
+      ICSSParseErrorHandler aRealParseErrorHandler = aSettings.getCustomErrorHandler ();
+      if (aRealParseErrorHandler == null)
+        aRealParseErrorHandler = getDefaultParseErrorHandler ();
 
       // Use the default CSS exception handler if none is provided
-      ICSSParseExceptionCallback aRealExceptionHandler = aSettings.getCustomExceptionHandler ();
-      if (aRealExceptionHandler == null)
-        aRealExceptionHandler = getDefaultParseExceptionHandler ();
+      ICSSParseExceptionCallback aRealParseExceptionHandler = aSettings.getCustomExceptionHandler ();
+      if (aRealParseExceptionHandler == null)
+        aRealParseExceptionHandler = getDefaultParseExceptionHandler ();
 
       final boolean bBrowserCompliantMode = aSettings.isBrowserCompliantMode ();
 
       final CSSNode aNode = _readStyleSheet (aCharStream,
                                              eVersion,
-                                             aRealErrorHandler,
-                                             aRealExceptionHandler,
+                                             aRealParseErrorHandler,
+                                             aRealParseExceptionHandler,
                                              bBrowserCompliantMode);
 
-      // Failed to interpret content as CSS?
+      // Failed to parse content as CSS?
       if (aNode == null)
         return null;
 
+      // Get the interpret error handler
+      ICSSInterpretErrorHandler aRealInterpretErrorHandler = aSettings.getInterpretErrorHandler ();
+      if (aRealInterpretErrorHandler == null)
+        aRealInterpretErrorHandler = getDefaultInterpretErrorHandler ();
+
       // Convert the AST to a domain object
-      return CSSHandler.readCascadingStyleSheetFromNode (eVersion, aNode);
+      return CSSHandler.readCascadingStyleSheetFromNode (eVersion, aNode, aRealInterpretErrorHandler);
     }
     finally
     {
@@ -1214,29 +1250,34 @@ public static CascadingStyleSheet readFromReader (@Nonnull final IHasReader aRP,
       aCharStream.setTabSize (aSettings.getTabSize ());
 
       // Use the default CSS parse error handler if none is provided
-      ICSSParseErrorHandler aRealErrorHandler = aSettings.getCustomErrorHandler ();
-      if (aRealErrorHandler == null)
-        aRealErrorHandler = getDefaultParseErrorHandler ();
+      ICSSParseErrorHandler aRealParseErrorHandler = aSettings.getCustomErrorHandler ();
+      if (aRealParseErrorHandler == null)
+        aRealParseErrorHandler = getDefaultParseErrorHandler ();
 
       // Use the default CSS exception handler if none is provided
-      ICSSParseExceptionCallback aRealExceptionHandler = aSettings.getCustomExceptionHandler ();
-      if (aRealExceptionHandler == null)
-        aRealExceptionHandler = getDefaultParseExceptionHandler ();
+      ICSSParseExceptionCallback aRealParseExceptionHandler = aSettings.getCustomExceptionHandler ();
+      if (aRealParseExceptionHandler == null)
+        aRealParseExceptionHandler = getDefaultParseExceptionHandler ();
 
       final boolean bBrowserCompliantMode = aSettings.isBrowserCompliantMode ();
 
       final CSSNode aNode = _readStyleSheet (aCharStream,
                                              eVersion,
-                                             aRealErrorHandler,
-                                             aRealExceptionHandler,
+                                             aRealParseErrorHandler,
+                                             aRealParseExceptionHandler,
                                              bBrowserCompliantMode);
 
-      // Failed to interpret content as CSS?
+      // Failed to parse content as CSS?
       if (aNode == null)
         return null;
 
+      // Get the interpret error handler
+      ICSSInterpretErrorHandler aRealInterpretErrorHandler = aSettings.getInterpretErrorHandler ();
+      if (aRealInterpretErrorHandler == null)
+        aRealInterpretErrorHandler = getDefaultInterpretErrorHandler ();
+
       // Convert the AST to a domain object
-      return CSSHandler.readCascadingStyleSheetFromNode (eVersion, aNode);
+      return CSSHandler.readCascadingStyleSheetFromNode (eVersion, aNode, aRealInterpretErrorHandler);
     }
     finally
     {
diff --git a/ph-css/src/main/java/com/helger/css/reader/CSSReaderDeclarationList.java b/ph-css/src/main/java/com/helger/css/reader/CSSReaderDeclarationList.java
index 3b358ee5..55b4ed51 100644
--- a/ph-css/src/main/java/com/helger/css/reader/CSSReaderDeclarationList.java
+++ b/ph-css/src/main/java/com/helger/css/reader/CSSReaderDeclarationList.java
@@ -50,7 +50,9 @@
 import com.helger.css.parser.ParseException;
 import com.helger.css.parser.ParserCSS30;
 import com.helger.css.parser.ParserCSS30TokenManager;
+import com.helger.css.reader.errorhandler.ICSSInterpretErrorHandler;
 import com.helger.css.reader.errorhandler.ICSSParseErrorHandler;
+import com.helger.css.reader.errorhandler.LoggingCSSInterpretErrorHandler;
 import com.helger.css.reader.errorhandler.ThrowingCSSParseErrorHandler;
 
 /**
@@ -74,6 +76,9 @@ public final class CSSReaderDeclarationList
   @GuardedBy ("s_aRWLock")
   private static ICSSParseExceptionCallback s_aDefaultParseExceptionHandler = new LoggingCSSParseExceptionCallback ();
 
+  @GuardedBy ("s_aRWLock")
+  private static ICSSInterpretErrorHandler s_aDefaultInterpretErrorHandler = new LoggingCSSInterpretErrorHandler ();
+
   @PresentForCodeCoverage
   private static final CSSReaderDeclarationList s_aInstance = new CSSReaderDeclarationList ();
 
@@ -102,9 +107,7 @@ public static ICSSParseErrorHandler getDefaultParseErrorHandler ()
    */
   public static void setDefaultParseErrorHandler (@Nullable final ICSSParseErrorHandler aDefaultParseErrorHandler)
   {
-    s_aRWLock.writeLocked ( () -> {
-      s_aDefaultParseErrorHandler = aDefaultParseErrorHandler;
-    });
+    s_aRWLock.writeLocked ( () -> s_aDefaultParseErrorHandler = aDefaultParseErrorHandler);
   }
 
   /**
@@ -131,9 +134,33 @@ public static void setDefaultParseExceptionHandler (@Nonnull final ICSSParseExce
   {
     ValueEnforcer.notNull (aDefaultParseExceptionHandler, "DefaultParseExceptionHandler");
 
-    s_aRWLock.writeLocked ( () -> {
-      s_aDefaultParseExceptionHandler = aDefaultParseExceptionHandler;
-    });
+    s_aRWLock.writeLocked ( () -> s_aDefaultParseExceptionHandler = aDefaultParseExceptionHandler);
+  }
+
+  /**
+   * @return The default interpret error handler to handle interpretation errors
+   *         in successfully parsed CSS. Never <code>null</code>.
+   * @since 5.0.2
+   */
+  @Nonnull
+  public static ICSSInterpretErrorHandler getDefaultInterpretErrorHandler ()
+  {
+    return s_aRWLock.readLocked ( () -> s_aDefaultInterpretErrorHandler);
+  }
+
+  /**
+   * Set the default interpret error handler to handle interpretation errors in
+   * successfully parsed CSS.
+   *
+   * @param aDefaultErrorHandler
+   *        The default error handler to be used. May not be <code>null</code>.
+   * @since 5.0.2
+   */
+  public static void setDefaultInterpretErrorHandler (@Nonnull final ICSSInterpretErrorHandler aDefaultErrorHandler)
+  {
+    ValueEnforcer.notNull (aDefaultErrorHandler, "DefaultErrorHandler");
+
+    s_aRWLock.writeLocked ( () -> s_aDefaultInterpretErrorHandler = aDefaultErrorHandler);
   }
 
   /**
@@ -739,23 +766,31 @@ public static CSSDeclarationList readFromReader (@Nonnull @WillClose final Reade
       final CSSCharStream aCharStream = new CSSCharStream (aReader);
 
       // Use the default CSS parse error handler if none is provided
-      ICSSParseErrorHandler aRealErrorHandler = aSettings.getCustomErrorHandler ();
-      if (aRealErrorHandler == null)
-        aRealErrorHandler = getDefaultParseErrorHandler ();
+      ICSSParseErrorHandler aRealParseErrorHandler = aSettings.getCustomErrorHandler ();
+      if (aRealParseErrorHandler == null)
+        aRealParseErrorHandler = getDefaultParseErrorHandler ();
 
       // Use the default CSS exception handler if none is provided
-      ICSSParseExceptionCallback aRealExceptionHandler = aSettings.getCustomExceptionHandler ();
-      if (aRealExceptionHandler == null)
-        aRealExceptionHandler = getDefaultParseExceptionHandler ();
+      ICSSParseExceptionCallback aRealParseExceptionHandler = aSettings.getCustomExceptionHandler ();
+      if (aRealParseExceptionHandler == null)
+        aRealParseExceptionHandler = getDefaultParseExceptionHandler ();
 
-      final CSSNode aNode = _readStyleDeclaration (aCharStream, eVersion, aRealErrorHandler, aRealExceptionHandler);
+      final CSSNode aNode = _readStyleDeclaration (aCharStream,
+                                                   eVersion,
+                                                   aRealParseErrorHandler,
+                                                   aRealParseExceptionHandler);
 
-      // Failed to interpret content as CSS?
+      // Failed to parse content as CSS?
       if (aNode == null)
         return null;
 
+      // Get the interpret error handler
+      ICSSInterpretErrorHandler aRealInterpretErrorHandler = aSettings.getInterpretErrorHandler ();
+      if (aRealInterpretErrorHandler == null)
+        aRealInterpretErrorHandler = getDefaultInterpretErrorHandler ();
+
       // Convert the AST to a domain object
-      return CSSHandler.readDeclarationListFromNode (eVersion, aNode);
+      return CSSHandler.readDeclarationListFromNode (eVersion, aNode, aRealInterpretErrorHandler);
     }
     finally
     {
diff --git a/ph-css/src/main/java/com/helger/css/reader/CSSReaderSettings.java b/ph-css/src/main/java/com/helger/css/reader/CSSReaderSettings.java
index 1e5e571b..c3a5f5cc 100644
--- a/ph-css/src/main/java/com/helger/css/reader/CSSReaderSettings.java
+++ b/ph-css/src/main/java/com/helger/css/reader/CSSReaderSettings.java
@@ -29,6 +29,7 @@
 import com.helger.commons.string.ToStringGenerator;
 import com.helger.css.ECSSVersion;
 import com.helger.css.handler.ICSSParseExceptionCallback;
+import com.helger.css.reader.errorhandler.ICSSInterpretErrorHandler;
 import com.helger.css.reader.errorhandler.ICSSParseErrorHandler;
 
 /**
@@ -50,6 +51,7 @@ public class CSSReaderSettings implements ICloneable <CSSReaderSettings>
   private ICSSParseExceptionCallback m_aCustomExceptionHandler;
   private boolean m_bBrowserCompliantMode = DEFAULT_BROWSER_COMPLIANT_MODE;
   private int m_nTabSize = DEFAULT_TAB_SIZE;
+  private ICSSInterpretErrorHandler m_aInterpretErrorHandler;
 
   public CSSReaderSettings ()
   {}
@@ -63,6 +65,7 @@ public CSSReaderSettings (@Nonnull final CSSReaderSettings aOther)
     m_aCustomExceptionHandler = aOther.m_aCustomExceptionHandler;
     m_bBrowserCompliantMode = aOther.m_bBrowserCompliantMode;
     m_nTabSize = aOther.m_nTabSize;
+    m_aInterpretErrorHandler = aOther.m_aInterpretErrorHandler;
   }
 
   /**
@@ -226,6 +229,35 @@ public CSSReaderSettings setTabSize (@Nonnegative final int nTabSize)
     return this;
   }
 
+  /**
+   * @return The special error handler to be used to interpret a successfully
+   *         parsed CSS. May be <code>null</code>. If this is <code>null</code>
+   *         the default error handler from {@link CSSReader} is used.
+   * @since 5.0.2
+   */
+  @Nullable
+  public ICSSInterpretErrorHandler getInterpretErrorHandler ()
+  {
+    return m_aInterpretErrorHandler;
+  }
+
+  /**
+   * Set a special interpret error handler for handling errors in successfully
+   * parsed CSS.
+   *
+   * @param aInterpretErrorHandler
+   *        The special error handler to be used. May be <code>null</code> to
+   *        indicate to use the default error handler from {@link CSSReader}.
+   * @return this for chaining
+   * @since 5.0.2
+   */
+  @Nonnull
+  public CSSReaderSettings setInterpretErrorHandler (@Nullable final ICSSInterpretErrorHandler aInterpretErrorHandler)
+  {
+    m_aInterpretErrorHandler = aInterpretErrorHandler;
+    return this;
+  }
+
   @Nonnull
   public CSSReaderSettings getClone ()
   {
@@ -241,6 +273,7 @@ public String toString ()
                                        .append ("CustomExceptionHandler", m_aCustomExceptionHandler)
                                        .append ("BrowserCompliantMode", m_bBrowserCompliantMode)
                                        .append ("TabSize", m_nTabSize)
+                                       .append ("InterpretErrorHandler", m_aInterpretErrorHandler)
                                        .toString ();
   }
 }
diff --git a/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSInterpretErrorHandler.java b/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSInterpretErrorHandler.java
new file mode 100644
index 00000000..57ecdd7e
--- /dev/null
+++ b/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSInterpretErrorHandler.java
@@ -0,0 +1,50 @@
+/**
+ * Copyright (C) 2014-2016 Philip Helger (www.helger.com)
+ * philip[at]helger[dot]com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.helger.css.reader.errorhandler;
+
+import javax.annotation.Nonnull;
+
+import com.helger.commons.annotation.Nonempty;
+import com.helger.commons.string.ToStringGenerator;
+
+/**
+ * An implementation of {@link ICSSInterpretErrorHandler} that does nothing.
+ *
+ * @author Philip Helger
+ * @since 5.0.2
+ */
+public class DoNothingCSSInterpretErrorHandler implements ICSSInterpretErrorHandler
+{
+  public DoNothingCSSInterpretErrorHandler ()
+  {}
+
+  public void onCSSInterpretationWarning (@Nonnull @Nonempty final String sMessage)
+  {
+    /* really do nothing :) */
+  }
+
+  public void onCSSInterpretationError (@Nonnull @Nonempty final String sMessage)
+  {
+    /* really do nothing :) */
+  }
+
+  @Override
+  public String toString ()
+  {
+    return new ToStringGenerator (this).toString ();
+  }
+}
diff --git a/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSParseErrorHandler.java b/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSParseErrorHandler.java
index 4176d76a..9242bb34 100644
--- a/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSParseErrorHandler.java
+++ b/ph-css/src/main/java/com/helger/css/reader/errorhandler/DoNothingCSSParseErrorHandler.java
@@ -38,21 +38,21 @@ public DoNothingCSSParseErrorHandler ()
   public void onCSSParseError (@Nonnull final ParseException aParseEx,
                                @Nullable final Token aLastSkippedToken) throws ParseException
   {
-    /* empty */
+    /* really do nothing :) */
   }
 
   public void onCSSUnexpectedRule (@Nonnull final Token aCurrentToken,
                                    @Nonnull @Nonempty final String sRule,
                                    @Nonnull @Nonempty final String sMsg) throws ParseException
   {
-    /* empty */
+    /* really do nothing :) */
   }
 
   public void onCSSBrowserCompliantSkip (@Nullable final ParseException ex,
                                          @Nonnull final Token aFromToken,
                                          @Nonnull final Token aToToken) throws ParseException
   {
-    /* empty */
+    /* really do nothing :) */
   }
 
   @Override
diff --git a/ph-css/src/main/java/com/helger/css/reader/errorhandler/ICSSInterpretErrorHandler.java b/ph-css/src/main/java/com/helger/css/reader/errorhandler/ICSSInterpretErrorHandler.java
new file mode 100644
index 00000000..6efc6496
--- /dev/null
+++ b/ph-css/src/main/java/com/helger/css/reader/errorhandler/ICSSInterpretErrorHandler.java
@@ -0,0 +1,47 @@
+/**
+ * Copyright (C) 2014-2016 Philip Helger (www.helger.com)
+ * philip[at]helger[dot]com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.helger.css.reader.errorhandler;
+
+import javax.annotation.Nonnull;
+
+import com.helger.commons.annotation.Nonempty;
+
+/**
+ * Special CSS error handler that is invoked during interpretation of a parsed
+ * CSS.
+ *
+ * @author Philip Helger
+ * @since 5.0.2
+ */
+public interface ICSSInterpretErrorHandler
+{
+  /**
+   * Called when an interpretation error or warning occurs.
+   *
+   * @param sMessage
+   *        The message text of the error.
+   */
+  void onCSSInterpretationWarning (@Nonnull @Nonempty final String sMessage);
+
+  /**
+   * Called when an interpretation error occurs.
+   *
+   * @param sMessage
+   *        The message text of the error.
+   */
+  void onCSSInterpretationError (@Nonnull @Nonempty final String sMessage);
+}
diff --git a/ph-css/src/main/java/com/helger/css/reader/errorhandler/LoggingCSSInterpretErrorHandler.java b/ph-css/src/main/java/com/helger/css/reader/errorhandler/LoggingCSSInterpretErrorHandler.java
new file mode 100644
index 00000000..e75c56f3
--- /dev/null
+++ b/ph-css/src/main/java/com/helger/css/reader/errorhandler/LoggingCSSInterpretErrorHandler.java
@@ -0,0 +1,61 @@
+/**
+ * Copyright (C) 2014-2016 Philip Helger (www.helger.com)
+ * philip[at]helger[dot]com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.helger.css.reader.errorhandler;
+
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.Immutable;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.helger.commons.annotation.Nonempty;
+import com.helger.commons.string.ToStringGenerator;
+
+/**
+ * A logging implementation of {@link ICSSInterpretErrorHandler}. So in case a
+ * warning or an error occurs, the details are logged to an SLF4J logger.
+ *
+ * @author Philip Helger
+ * @since 5.0.2
+ */
+@Immutable
+public class LoggingCSSInterpretErrorHandler implements ICSSInterpretErrorHandler
+{
+  private static final Logger s_aLogger = LoggerFactory.getLogger (LoggingCSSInterpretErrorHandler.class);
+
+  /**
+   * Default constructor.
+   */
+  public LoggingCSSInterpretErrorHandler ()
+  {}
+
+  public void onCSSInterpretationWarning (@Nonnull @Nonempty final String sMessage)
+  {
+    s_aLogger.warn (sMessage);
+  }
+
+  public void onCSSInterpretationError (@Nonnull @Nonempty final String sMessage)
+  {
+    s_aLogger.error (sMessage);
+  }
+
+  @Override
+  public String toString ()
+  {
+    return new ToStringGenerator (this).toString ();
+  }
+}
diff --git a/ph-css/src/test/java/com/helger/css/parser/ParserCSS30Test.java b/ph-css/src/test/java/com/helger/css/parser/ParserCSS30Test.java
index 93034f4e..f21f13b3 100644
--- a/ph-css/src/test/java/com/helger/css/parser/ParserCSS30Test.java
+++ b/ph-css/src/test/java/com/helger/css/parser/ParserCSS30Test.java
@@ -27,6 +27,7 @@
 import com.helger.css.decl.CascadingStyleSheet;
 import com.helger.css.decl.ICSSTopLevelRule;
 import com.helger.css.handler.CSSHandler;
+import com.helger.css.reader.CSSReader;
 
 /**
  * Test class for class {@link ParserCSS30}.
@@ -56,7 +57,9 @@ public void test2 () throws ParseException
     final CSSNode aNode = aParser.styleSheet ();
     assertNotNull (aNode);
 
-    final CascadingStyleSheet aCSS = CSSHandler.readCascadingStyleSheetFromNode (ECSSVersion.CSS30, aNode);
+    final CascadingStyleSheet aCSS = CSSHandler.readCascadingStyleSheetFromNode (ECSSVersion.CSS30,
+                                                                                 aNode,
+                                                                                 CSSReader.getDefaultInterpretErrorHandler ());
     assertNotNull (aCSS);
 
     for (final ICSSTopLevelRule aTopLevelRule : aCSS.getAllFontFaceRules ())
diff --git a/ph-css/src/test/java/com/helger/css/supplementary/issues/Issue33Test.java b/ph-css/src/test/java/com/helger/css/supplementary/issues/Issue33Test.java
index 07fdf197..d32c8ea9 100644
--- a/ph-css/src/test/java/com/helger/css/supplementary/issues/Issue33Test.java
+++ b/ph-css/src/test/java/com/helger/css/supplementary/issues/Issue33Test.java
@@ -16,30 +16,40 @@
  */
 package com.helger.css.supplementary.issues;
 
+import static org.junit.Assert.assertEquals;
+
 import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import com.helger.css.ECSSVersion;
 import com.helger.css.decl.CascadingStyleSheet;
 import com.helger.css.reader.CSSReader;
 import com.helger.css.reader.CSSReaderSettings;
+import com.helger.css.reader.errorhandler.DoNothingCSSInterpretErrorHandler;
 import com.helger.css.writer.CSSWriter;
 import com.helger.css.writer.CSSWriterSettings;
 
 /**
- * Test for issue 26: https://github.com/phax/ph-css/issues/33
+ * Test for issue 33: https://github.com/phax/ph-css/issues/33
  *
  * @author Philip Helger
  */
 public final class Issue33Test
 {
+  private static final Logger s_aLogger = LoggerFactory.getLogger (Issue33Test.class);
+
   @Test
   public void testIssue ()
   {
+    // No log message may be issued in this test!
+
     final String css = "@media \\0screen\\,screen\\9 {.test {margin-left: 0px}}";
     final CSSReaderSettings aSettings = new CSSReaderSettings ().setCSSVersion (ECSSVersion.LATEST)
-                                                                .setBrowserCompliantMode (true);
+                                                                .setBrowserCompliantMode (true)
+                                                                .setInterpretErrorHandler (new DoNothingCSSInterpretErrorHandler ());
     final CascadingStyleSheet cascadingStyleSheet = CSSReader.readFromStringStream (css, aSettings);
     final CSSWriter writer = new CSSWriter (new CSSWriterSettings (ECSSVersion.LATEST, true));
-    System.out.println (writer.getCSSAsString (cascadingStyleSheet));
+    assertEquals ("@media \\0screen\\,screen\\9 {.test{margin-left:0}}", writer.getCSSAsString (cascadingStyleSheet));
   }
 }