In IE version 6 (firefox is OK, haven't tested any others), if you have multiple code decalartions in your post that go off to the side, the scroll bar will be at the bottom of the post, instead of at the specific box for the code that needs to be scrolled. See this post to see an example of what I mean:
http://forum.joomla.org/index.php/topic,10762.0.html
Compare what that looks like in Firefox vs. IE.