Add this to make it work in IE 6:
body{
padding: 0;
margin: 0;
width: 100%;
height: 100%;
}
Since the body didn't have specified dimensions before, IE didn't know what
to base the 100% off of for the cover div. Kinda lame, but thus is IE. The
good news is that IE 7 doesn't have the same problem.
Jon