I've found more sites that don't display properly on Firefox than I have for IE.
Actually, I have yet to see a webpage display improperly on IE, with you know, something newer than IE6.
I have personally made a small website that follows all standards. It displayed fine on everything but IE. Websites only work on IE because people use IE because they know nothing about web browsers, and simply click "internet." I have talked to many people with whom this is the case.
Basically now days most large websites make two versions, one for IE and one for web browsers that actually follow standards. Besides, I have a nice little extension for chrome that will open the current page I'm on using internet explorer, but still have it within the chrome window. I used it for the first time yesterday to play instant action, which I found out wasn't even needed as it runs fine within chrome.
Edit: Oh, and you're just thinking virus security. Honestly I have to say you've been horribly lucky with viruses, or your virus scanner isn't working. Beyond virus security, there is warning about phisher scams and more that many browsers other than Ie give. While this may not be as relevant to you or me, it certainly is a very big concern when telling your parents or other people which browser to use.
