Merge pull request #26499 from ht-l1/contents-update-4

Advanced Selectors: adding a disclaimer on the usage of single colon vs double

intermediate_html_css/intermediate_css_concepts/advanced_selectors.md

@@ -257,7 +257,7 @@ To see what other things you can achieve with attribute selectors, such as searc
 
 <div class="lesson-content__panel" markdown="1">
 1. Complete [CSS Diner](https://flukeout.github.io/). You should be familiar with most of the content in the first couple of exercises, but practice and review never hurt! Don't forget to read the examples and explanations on the right.
-2. Read [Shay Howe's article on Complex Selectors](https://learn.shayhowe.com/advanced-html-css/complex-selectors/). This covers most of the content of this lesson in a bit more detail.
+2. Read [Shay Howe's article on Complex Selectors](https://learn.shayhowe.com/advanced-html-css/complex-selectors/). This covers most of the content of this lesson in a bit more detail. As stated in their article, they sometimes use a single colon instead of a double one for pseudo-elements. Please keep in mind that the double colon is now the standard.
 </div>
 
 ### Knowledge check