Firefox

Simply put, the best browser I've seen. I swore by Opera for several years, even though it didn't support all the web features that some web designers take for granted. Mozilla (combined email and web browser) didn't impress me too much either. But now they have broken off the browser, named it Firefox, and according to the reviews, it's giving Internet Explorer something to worry about. And because it isn't Internet Explorer, using it will help keep your machine free of viruses and ad/spyware.