The box's position (and possibly size) is specified with the
left properties. These properties specify offsets with respect to the box's containing block. Absolutely positioned boxes are taken out of the normal flow. This means they have no impact on the layout of later siblings. Also, though absolutely positioned boxes have margins, they do not collapse with any other margins.
One can apply margins on a absolutely positioned box. Here we would get the same result with no margin and
bottom:0 instead of top:100%.
In IE6, the yellow box is not painted across the viewport, instead it shrinkwraps around its content.
Reduce the height of the viewport until it shows a vertical scrollbar, then style
Style the yellow box with:
top: 0; bottom: 0; height: auto;