It's not often you see people benchmarking browsers. Futuremark wants to change that with the public beta release of Peacekeeper.
Futuremark's aim with this benchmark is to put an end to the so-called "browser wars" by removing subjective opinions or analysis of performance with too much room for variability such as loading times.
In order to have more basis on real world performance, each of the tests are weighted differently depending on how heavily they are used on commonly accessed websites such as YouTube and Facebook. A few tests, such as those using arrays, are not based on these website profiles.
Of course, these websites do not represent all website designs, and are built with heavy load in mind and optimized to work on most computers. Performance differences between browsers as determined by Peacekeeper may not reflect the performance you see on the websites you visit.
Peacekeeper also has a simplified Online Result Browser which shows average browser scores for commonly used processors.