Internet Explorer 8 is the fastest browser, based on benchmark testing conducted in a Microsoft lab.
A white paper published by Microsoft states that in a ‘real world’ test on browser speeds, Microsoft's team compared the performance of IE 8 (currently available as Release Candidate 1), Google Chrome 1.0 and Mozilla Firefox 3.05. Microsoft has made available a video on the study as well as a whitepaper, "Measuring Browser Performance: Understanding Issues in Benchmarking and Performance Analysis".
For the purpose of the benchmarking, Microsoft used 25 popular Web sites, based on a comScore ranking. The results clearly showed that IE 8 was the fastest browser at 12 sites, followed by Chrome (nine sites) and Firefox (four sites).
Microsoft also added that in addition to the exceptional page load performance, Internet Explorer 8 is also optimized to speed up the things that many users do day in and day out such as mapping an address, emailing links to friends, checking the weather, monitoring eBay auctions, etc.
Internet Explorer 8 can perform these tasks using anywhere from 10-50% fewer steps than other browsers.