If you’ve installed Google Chrome and Firefox browser on your computer, the Google Toolbar 5 for Firefox, once installed adds a "new tab" page from Chrome. When you open a new tab, the page shows 9 thumbnails of the most frequently visited pages, recent bookmarks and pages from recently closed tabs, similiar to Opera “speed dial” feature. Unlike the similar feature from Google Chrome, you can disable the page and you can remove the thumbnails you don't like, explains Google.

Source:→ Google System