Your wrapper is min-width: 950px; the left and right columns are 180 + 2*10px padding = 2*200px leaving a space of 550px.
Your #centercol has side padding of 200px which increases its width to 920px so it doesn't fit in the middle space of 550px in IE7 ( Firefox guessed that you didn't mean that) so change the padding to margin which allows the side columns to fit in the margins
#centercol {
position:relative;
/*padding:0 200px;*/ margin: 0 200px;
min-width: 520px;
}
You also have an unclosed comment here (which wasn't part of the problem)
#rightcol {
position:relative;
top:-10px;
right:-10px;
float:right;
/* width:200px; /* for IE5/WIN */
width:180px; /* actual value */
margin:0 0 -10px 0;
padding:10px;
z-index:99;
}
which should be
#rightcol {
position:relative;
top:-10px;
right:-10px;
float:right;
/* width:200px;*/ /* for IE5/WIN */
width:180px; /* actual value */
margin:0 0 -10px 0;
padding:10px;
z-index:99;
}
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.