I've just noticed a project in a company I'm working in that says - Supports IE6 only.
Sure enough, I've opened it up in an IE 8 and Chrome and the Buttons and the text were way off their original positions, and basically all sense of formatting was gone.
I'm not authorized to see the code yet, but I was wondering what the differences in rendering basic HTML / Javascript are between IE 6 and IE 8?
I saw this once with a previous job. The site only worked in IE 6 because of some third party bought page editing app of the site that they couldnt seem to let go of or replace with something better/compatible. It was the sole reason nothing moved to IE 7 at the time. Not an answer to your final question, but just to let you know that you are not the only one who has experienced/supported an IE 6 only website.
This is happening because rendering mechanism in ie6 & ie8 are different. First get the code and go through below link you will get the exact problem with your code.
http://blogs.msdn.com/ie/archive/2009/03/12/site-compatibility-and-ie8.aspx
Jitendra