Say I want to post the link: http://en.wikipedia.org/wiki/Jeff_Atwood#External_links
If I create a text link using the hyperlink button, and paste in the above link, it becomes:
http://en.wikipedia.org/wiki/Jeff_Atwood%23External_links
The # was replaced with %23. Unfortunately, some webpages can’t handle that switch as well as Wikipedia, so links break.