Internet Explorer as a whole does not display xhtml/css correctly. IE7 is a lot closer which is why it looks more like what your Firefox output looks like. Try checking your tags for position, padding, and margin as those 3 seem to effect the differences the most. You can also try using a different stylesheet for IE6 ... Magento has this functionality built in. The site *should* detect which browser is being used and pull a different stylesheet if necessary. Look in your css folder and you’ll see the file for it.