Style links depending on url or file format

While browsing at Forrst I came across this piece of CSS.

a[href^="http://"] { color: blue; }
 
a[href^="mailto:"] { color: red; }
 
a[href$=".pdf"] { color: green; }

Styling links depending on their formats.

ajcates said:
For the sake of usability and consistency instead of changing the color on links based on their format I often times use this technique instead to add on little file icons.