Even though IE5PC gets the box model WRONG according to the W3C spec, I actually like their way of doing it better. It makes it MUCH easier to add up percentages. With the spec's version of the box model, if I have two boxes side by side of equal width, I could set them at 50% each and be happy. But… if there is a border, a margin or some padding involved, I have to decrease that 50% value to account for those elements. However, those elements are generally NOT calculated by percentages, because it just doesn't look right. How do you subtract (2px) + (10% * 2) + (4ex * 2) from 50%? Yeah… exactly… you can't. So you guess. However… once you start increasing/decreasing the width of your browser, things get a little screwy. You get extra space where you didn't want it, things become uncentered, and eventually, float elements push other float elements out of the way to make more room. I could make DIV's on the outside with the correct percentage points (and no margins, padding or border) and place DIVs inside those with the actual content desired and the width set to 100%, but that would involve using markup for layout's sake which I don't want to do and is one of the biggest reasons for using CSS to begin with.
