On http://darrenwilson.com the main content box is anchored at 32,32 and set to 480px wide. The sidebar content box is anchored at 496px, which should result in it hanging 16px to the right of the main content box. Instead, it overlaps. This indicates to me that Mozilla is drawing the box contents at 480px wide, then adding 16px of padding on the outside of that, and then drawing the box border outside of that. My 480px box is now 514px wide. (480px + 16px padding left + 16px padding right + 1px border left + 1px border right) Box dimensions should be absolute, shouldn't they? In my view, padding and border properties should not affect the overall outside dimensions of the container itself, just the available area left inside the container for content.
The CSS width property applies to the content width, not the box width. You must take padding, border, and margin width into consideration as well to determine overall box width. See [http://www.w3.org/TR/ REC-CSS2/visudet.html#the-width-property], as well as the box model diagram at [http://www.w3.org/ TR/REC-CSS2/box.html#box-dimensions]. Resolving Invalid.