The Firefox 4 beta program is up to beta 10 so I decided to try Firefox 4. No big improvements in the sites I visit and some small errors remaining. Firefox 4 will be of more use when stupid Web developers fix rubbish code.
Firefox 3 does not handle the video element in from HTML 5 so you upgrade to Firefox 4. Then you find some Web site developers artificially restrict access to video. They make stupid assumptions about which browsers handle HTML 5 video. You are stuck with a Web site treating Firefox 4 as Firefox 3. The Web site decides you cannot view video so you must use Flash. Of course you have Flash switched off because Flash is dangerously insecure, bug ridden, and obsolete. You do not get to watch all those fancy videos in Firefox 4.
I found one bug in the first few seconds. Selecting a bookmark and choosing Open works. Open in a New Tab and Open in a New Window do not work. Everything else looks the same.
Tabs were moved up one line but the total vertical space wasted is still the same. Firefox could easily move the menu bar up onto the top line to make better use of the very wide short screens almost all computer manufacturers force down our throats. Operating systems let us move bars to the side to fit the wide screens. Why not Firefox?