Highlighted Footnotes like Wikipedia with CSS

You may have noticed on Wikipedia when you click a footnote, the footnote is highlighted to visually indicate which one you should be looking at. This can be done using CSS’s :target pseudo-class.

In your main content, you might have a paragraph of text with a footnote where the HTML looks like this:

<sup><a href="#one" id="cite-1">[ 1 ]</a></sup>
Code language: HTML, XML (xml)

Notice the ID attribute. This will be used in the footnote so the reader can easily click to visually indicate where they left off in the main content. In addition, each footnote will have a link next to it that points back to the main content, along with the footnote content that also has the ID attribute present:

<ol>
    <li id="one"><a href="#cite-1">^</a> [Footnote content]</li>
    <li id="two"><a href="#cite-2">^</a> [Footnote content]</li> 
    ... 
</ol>
Code language: HTML, XML (xml)

The CSS is simple (in this case, it includes a CSS transition):

:target { 
    background: #ccc;
    border: solid 1px #aaa;
    transition: all .8s; 
}
Code language: CSS (css)

Here’s a live demo: