If you try to post a code like this one:
<div id="x">this image will have cool CSS stuff</div> inside a wordpress post, or static page (using the post news panel) only using the code tab, it will work fine.
But if you ever try to edit that post again, later on...
all your divs will be transformed into `<p>´
I wander if WordPress 2.3.3 still does that, or we now have some kind of option NOT to replace any coding from our posts.