Why does my site look different in IE than in Firefox
Not completely in-depth, but it gives a general idea of what is going on. The bigger picture is also that various browser versions of IE will also render your CSS layouts differently. For example, IE 5.5 and IE 7.0 although still IE, render CSS layouts differently.
One such example is the Box Model – http://en.wikipedia.org/wiki/Internet_Explorer_box_model_bug.
Browser support by element – http://www.quirksmode.org/css/contents.html
General IE workaround site – http://www.positioniseverything.net/
IE7 should render rather closely to other modern browsers like Safari, Firefox, Opera, etc. Keep in mind that IE6 is from 2001 (that’s pretty old in software terms!) and will be around for a while…