It's helpful to give more specific feedback if you can.

Here's the process to roll back:

First, I recommend backing up your Firefox settings in case something goes wrong. See Backing up your information (copy your whole profile folder).

Next, download and save Firefox 3.6 to your desktop for future installation. http://www.mozilla.com/firefox/all-older

Close Firefox 4, and uninstall it. Do not remove your personal data and settings, just the program.

Then finally you can reinstall Firefox 3.6. Unless you have installed an incompatible add-on, it should pick up where you left off. If there are serious issues, please post back with details.

Note: I haven't actually tried this myself!

OK thanks will get back to this later and let you know

Hello, have read all the information, I don't fancy the bit about serious issues, so think I'll just go back to explorer it seems easier

Maybe you'll prefer Firefox 5 when it comes out this Fall?