Firefox 4 beta which was released yesterday has many new features and one of them is the support for Windows 7 taskbar jumplist. From the jumplist, you can open new Firefox tab, new session and also private browsing. Apart from this, there is also frequent list which shows most frequently accessed sites in Windows 7 taskbar jumplist. In case you do not use the frequent lists, you can easily disable them on Firefox 4.
To disable, frequent list, open config, by typing about:config in the Firefox navigational URL. Click on “I’ll be Careful. I promise” button. In the filter type taskbar and you can see an entry “browser.taskbar.lists.enabled” option. The present value would be true, double click to make it false.
Once the value is disabled, you can see frequent lists removed from the Windows 7 jumplist for Firefox.
If you want to enable it again, make the value back to true.