User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; it; rv:1.9.1b99) Gecko/20090605 Firefox/3.5b99 (.NET CLR 3.5.30729) Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 6.1; it; rv:1.9.1b99) Gecko/20090605 Firefox/3.5b99 (.NET CLR 3.5.30729) Adds Win 7 Taskbar full compatibily to show additional functions when users click mouse right-button in the window's icons. This behavour can be visible in some native program, like IE, MSN. For istance, implemeting this feature it can show users open tabs, lastes page opened, etc. Reproducible: Always

There are several bugs opened for this, please search first. The meta bug is bug 474052. The one that looks the most like this one is bug 473045, but there are others.