Nice write-up. I would like to add one more thing: in certain cases, IE6 automatically applies a “clear: both” style to a non-floating element that sits below a floating element, whereas in other browsers (tested on Chrome 2 Beta), the “clear: both” style has to be explicitly added to the stylesheet for the non-floating element. I noticed this when I tried to fix IE6′s rendering of this template:

http://www.freelayouts.com/templates/Hosting-Website-Template?preview=true

In Chrome it renders fine, but it’s broken in IE6. Fixing the right column box wrapping issue was trivial (reduce width values for IE6), but fixing the issue where the Beginner/Business/Premium Plan boxes were pushed down too far took a little more effort to debug. In order to fix this so that the page renders the same in both Chrome and IE6, I had to remove the “margin-top: 170px” style and add “clear: both” to #boxes.