Now you'll never need IE again...
I just recently found a very cool extension for FireFox. It's called IETab and it allows you to load an instance of IE inside a FireFox tab. Now, when you go to a site that says it requires IE, you can simply use this extension to load the site in FF. Here's some info from the Mozilla Extensions site:
IE Tab - an extension from Taiwan, features: Embedding Internet Explorer in tabs of Mozilla/Firefox. If you need some instructions. Please visit our official website on http://ietab.mozdev.org
This is a great tool for web developers, since you can easily see how your webpage displayed in IE with just one click and then switch back to Firefox.
Enjoy!!