Add info re links

STYLE_GUIDE.md

@@ -36,3 +36,36 @@ For example:
 
 !!! note
     This is a note.
+```
+
+## Internal Links
+
+MkDocs automatically adds an html anchor to all headers. The default anchor is the header text in lower case and spaces replaced by `-`. So, the header 'Internal Links' gets an automatic anchor of `internal-links`. (Note too that multiple `-` characters, e.g. `--robot`, in a header will be truncated to a single `-` in the anchor.)
+
+We can manually specify the anchor by adding an attribute, so:
+
+``` markdown
+## Internal Links {: #anchor }
+```
+
+The standard MkDocs method to link to another page is by reference to the relative path to the markdown file:
+
+``` markdown
+[link text](page.md)
+```
+
+and to a section within the page with
+
+``` markdown
+[link text](page.md#anchor)
+```
+
+The EasyBuild docs uses [mkdocs-autorefs](https://github.com/mkdocstrings/autorefs). This allows internal links to be automatically linked by referring only to the anchor, e.g.
+
+``` markdown
+[link text][anchor]
+```
+
+N.B. according to the *mkdocs-autorefs* README:
+
+> Note that this plugin's behavior is undefined when trying to link to a heading title that appears several times throughout the site. Currently it arbitrarily chooses one of the pages.