Does look like a CSS problem. It looks like a float bug, which IE8 doesn't tend to suffer from, but it might be operating in 'Quirks mode' (see
http://www.quirksmode.org/css/quirksmode.html). The site doesn't seem to be in quirks mode, but I can't reach the page you've shown there.
Without seeing the code it's hard to say, but it looks like a float margin or padding problem in CSS.