As a fan of Firefox, I have been following it for 6, 7 years. A window poped up this morning showing the Firefox 4.0 is available now after I lauched the Firefox. With no doubt, I upgraded my Firefox to 4.0 right away.
I simply poked around and found the obvious improvements – faster speed and better user interface. Another new feature I like is the ‘App Tab’. It allows me to give a permanent home to the sites I alway keep open in the tab bar, like mail, facebook, my blog.