The Viamatic Tabnail extension is an extension which you should use if you have a slow internet connection. It lets you preview the pages as they load in realtime. It adds thumbnail of the page that is being loaded into the tab and updates it in realtime. If you have a broadband connection this extension might not be for you. If you find it usefull please do rate it on mozilla.org
If you use TabMix plus or some other extension which changes the tabs this extension might not work, and so far there is no work around for this problem.
If you have any support questions or comments post them in the tabnail forum .