I love posts like this. It's just about adding a little icon to the end of certain links, but it ends up touching on a million things along the way. I think this is an example of why some people find front-end fun and some people rather dislike it.
Cool [attribute] selectors that identify off-site links
Deliberating on whether it's OK to use additional HTML within links or not
Usage of white-space
Combining margin-left and padding-right to place icons into placeholder space