Bugged Internet Explorer

We got a webs开发者_运维百科ite (happened before too) that when viewed on IE8 on 2 PC don't show as supposed, but when tested on 2 other PC using same Windows, same IE version show correctly...

I did a quick draw (pardon Ms-Paint for the bad compression/gradient), the first part (pink with red border) is the background as I see it on every browser on 4 different PC, the second part is what I see on those 2 PC. The white box (with black border) is a div which is over the pink one, but this DIV has no background, it should not "cut/hide" the other background.

So there is my question, what could cause this in general? And why those 2 PC have problem specific to them, is that possible that IE Rendering Tool have been corrupted/bugged in some sort.

Press F-12 to open the debugger and determine which rendering mode the page is using. Make sure you're not in "quirks mode".