I – Disable Tab Scrolling

Firefox 2 sets a fixed minimum width for tabs, so rather than constantly shrinking when your tab bar is filled, tabs spill off the screen into a dropdown; a behavior reminiscent of XP’s default ‘Group similar taskbar buttons’ setting. If like me you find this thoroughly unusable, it can be disabled.

1. Hop into Firefox’s manual configuration by typing about:config into the address bar.
2. Enter browser.tabs.tabMinWidth into the ‘filter’ box, and double click on the browser.tabs.tabMinWidth value, which appears under ‘Preference Name’.
3. Enter 0 as the value.

Now restart Firefox, to open as many tabs as you like without the irritating dropdown!

Tip via: Life Hacker.

II – Kill the close tab button

Another dubious ‘innovation’ in FF2, is a close tab button located on each individual tab. If like me, you use middle click to both open links in a new tab, and close individual tabs, these X’s are superfluous and distracting. To remove them..

1. Again open Firefox’s manual configuration by typing about:config into the address bar.
2. Enter Browser.tabs.closeButtons into the ‘filter’ box, and double click on the Browser.tabs.closeButtons value which appears under ‘Preference Name’.
3. The value you enter next determines how Firefox displays the close tab X
– To remove close tab buttons altogether, enter 2.
– To display a single close button in the active tab (IE7 style), enter 0.
– To display a single close button on the right, which will close the active tab, enter 3.
– To restore the default, close button in each tab, behavior, enter 1.

Tip Via: Mozillazine.

III – Enable Session Saver

Anyone who has used the Session Saver plugin with previous versions of Firefox, will have become addicted to the ability to quit the browser and open it up once again, with all tabs you were working on restored. To enable similar behavior in Firefox 2..

1. Click on 'Tools' then select 'Options'.
2. In the 'When Firefox starts' drop down box, select 'Show my windows and tabs from last time'.

For the advanced features of the Session Saver plugin – such as saving and restoring a collection of tabs, we’ll have to wait for the official update for FF2.

IV – Old Firefox Theme

What is the deal with the new Firefox theme? It is quite simply, ugly; luckily, there are alternatives. If like me you preferred the FF1.* theme, Florian Schmitz has come you your rescue with his Winstripe Theme. Alternately, you may prefer the more futuristic style of Grey Modern, an update of the Mozilla browser’s ‘Modern’ skin. If you’re a Mac user, try customizing to fit in with OSX, with the GrApple (Eos Pro) theme.

Once you’ve installed a theme..
1. Click 'Tools', then select 'Add-ons'.
2. Click 'Themes'. Now select the theme you wish to use and click the 'Use Theme' button. Now restart Firefox to enjoy your new browsing environment.

Update: I’ve just come across a post on Life Hacker which details almost all these tweaks and a few more to boot.