Now if only we could get rid of the problems with Mozilla. It has its own set of CSS problems - some of which actually work fine in IE 6 (and Safari/WebKit). But don't get me started on Opera. I don't know how well its cutting edge betas are doing, but previous versions always had some issues. Not the least of which was pretending to be IE. Opera is about as far from being a recommended browser as IE 6 in my books.

In any case, IE inserts extra space in places most other browsers do not. I'm not certain this is breaking any spec, it may be something that's simply undefined. This happens on normal pragraphs and other elements as well (going from memory here).

If you're not using CSS then you might as well give up on trying to match the layouts so closely between different browsers. You should also avoid using BR for anything but to force a new line - don't use it for spacing. If you want space, start a new paragraph.

Once you start heavily using/relying on CSS you'll almost stop caring about the contents on the actual markup part of the layout.