Zdnet has just pointed me towards Microsoft’s Internet Explorer 8 Compatibility View List for Windows Vista which lists all the websites IE 8 is known to have problems with: and it’s extensive (see this Zdnet list for a human-readable display). I did a quick search for most of the major sites and they all seem to be listed: From Microsoft.com (if they can’t get their own site working in their own software it doesn’t bode well), all Amazon sites (.com and .de, .cn and .co.uk etc), all major social networking sites (Facebook.com, MySpace.com, LinkedIn.com and Twitter.com are all listed), to all of Google, bbc.co.uk, Paypal.com , all of eBay and many many more. And this is only the 2,400 major sites that Microsoft have found to have problems with IE8 (or should that be: sites that Microsoft have found that IE8 is broken on).
All the more reason to drop Internet Explorer and try Firefox, Safari, Opera or another browser of your choice (mine’s Firefox)