Firefox 4 integrates better with some Windows 7 features, including taskbar tab previews, download progress bar in the taskbar icon, and jumplists. Here are some way to enable, disable or customize the different options.
1. Enable taskbar previews.
In the Firefox menu, select the Options item to open the Options dialog. Change to the Tabs page and enable Show tab preview in the Windows taskbar.
2. Customize Firefox’s jumplist.
When you right-click on Firefox taskbar icon it displays, by default, your most frequently visited pages (some of which you can pin to the pinned section of
the jumplist by clicking on the pin button next to the site), some common tasks like opening a new tab or window, and taskbar related commands.
If you find the Tasks section useless, you can hide it: go to about:config, search for taskbar, and set browser.taskbar.lists.tasks.enabled to false by double-clicking it.
To hide the Frequent section set browser.taskbar.lists.frequent.enabled to false by double-clicking it. Note, however, that this will enable the Recent section no matter the value of browser.taskbar.lists.frequent.enabled which is set to false by default.
3. Pin a tab to the jumplist.
Finally, to add a page to the Pinned section in the taskbar, simply drag the favicon (from the site button) to Windows taskbar.