Safari is undoubtedly one of the fastest browsers available, even if iBench 5.0 delivers slightly optimistic scores (the SunSpider JavaScript benchmark does not seem to be affected). Under both Mac OS X 10.5.2 and Windows Vista SP1, Apple's browser is a front-runner.

The worst-performing browser in our tests is Internet Explorer 7 — The SunSpider JavaScript benchmark, in particular, shows up the deficiencies of Microsoft's current browser. Things may change with Internet Explorer 8, as the first beta version shows a significant performance improvement. However, the competition is not standing still, with new versions of Firefox (3) and Opera (9.5) closer to release than IE 8.

Overall, and taking the performance of the beta versions into consideration, the browser performance rankings are as follows: Firefox and Safari in a clear lead ahead of Opera and finally Internet Explorer. Firefox 3, due in June, promises very good performance and efficient memory usage. No browser used less memory to open multiple sites than the Beta 5 version of Firefox 3, and only a few sites failed to display correctly. Safari and Opera, however, are more likely to exhibit incompatibilities.

These tests show that when it comes to browser performance, there's plenty of scope for improvement. In some tests, we observed speed boosts of the order of 100 per cent between the current version and the latest beta.