How dows one test browser speed?

This really isn’t a support question so I hope it is in the right place.

Yesterday I installed the Alfa release of Firefox 4 (code name Minefield 3.7a5pre) for testing.

It feels faster than Firefox 3.5 (I think that’s what I’m using currently)

How do I go about finding numbers to validate or disprove my feeling?

Maybe this is a nice one for you: Internet Browser Software Review 2010 - TopTenREVIEWS

I’m using Opera’s weeklies on my laptop, talking about speed…

This is a javascript benchmark test which allows direct comparison between results in different browers:
SunSpider JavaScript Benchmark
Of course javascript is not everything.