Firefox is lauded by fans for its download speed and a superior user interface, and users say that its pop-up blocker is one of the best out there. It offers tabbed browsing, which means that users can jump back and forth between different sites with only one window open, and live bookmarks, which show users the most recent headlines on their favorite sites and lets them go directly to those articles.
But the biggest challenge facing anyone who wants to take on IE is that most Web sites are built to work best with Microsoft's IE simply because it's what sits on most PCs. That means some sites may not look quite right or may not be accessible at all via a browser other than IE.
>>>copied from a google search