Highlighting

I am having trouble highlighting. I can click favorites and the list will not stay highlighted when I go down the list to pick a URL. I am having a problem if I have gone to say three sites and I want to return to the previous site. If I click the back button the browser will return to the first site and jump the previous site. I am using firefox as a browser but it seems to be the same in internet explorer. I have windows 7. I have another computer with Vista that does not have the problem.