To try the thousands of add-ons available here, download Mozilla Firefox, a fast, free way to surf the Web!Close
Welcome to Firefox Add-ons.
Choose from thousands of extra features and styles to make Firefox your own.Close
Rated 4 out of 5 stars
What GoWebFish said underneath.
But you also have to make sure the "On for All web Pages" function of Firebug is ticked(enabled) if it was disabled.
That triggered yslow to work after trying for the ... time