I used this extension. At first, it was good and it gave me a blank new tab as I wished. Unless it occupied a huge space in the address bar (that even I could not sometimes find the actual address on the net), I was satisfied. But, after two weeks, I saw my Firefox working terribly, all icons were trembling when I was opening a new tab, it was truly irritating! After I removed this extension I saw Firefox is OK again. I do not know why it happened, just I know there was something wrong.