Page Speed is an YSlow alternative for testing and optimizing websites. I tested it only briefly on Firefox 3.5b4 (officialy, it does not support beta Firefox releases, but you can always unpack the XPI and change the maxversion attribute.
Both YSlow and Page Speed require the excellent Firebug extension, which is an essential tool for web developers. If you don’t know YSlow or Page Speed yet, now is the time to get acquainted.
