Firefox 5 allows users to preview all the open tabs in taskbar on a Windows 7 system. This feature can be enabled using the Firefox Options menu. To launch Firefox 5 options window, Click the drop down arrow below Firefox then navigate to Options side menu and select Options from the list
In the Options window, navigate to Tabs and mark the checkbox with label as Show tab previews in the Windows Taskbar.
Click OK button to confirm and save the changes. Now placing the mouse on the Firefox icon in Windows Taskbar would display the previews of all the opened tabs as shown below.