Gold Navigation

How can I delete sights visited from the drop down?

I use Mozilla. The drop down in the navigation toolbar shows the same twelve sights visited in the past followed by a gold star. Most of them are sights that I bookmarked but not all. I highlight each one and hit delete but they return. How can I delete them and prevent them and any others from returning?
Thanks for the help, but none of it worked.

hehe, go to your browser(the one you want to clear)..firefox, Explorere, etc..

Click tools, then clear private data. check all boxes, and press ok.. if that doesnt work. Go to tools, options, privacy and clear the data in there. even cookies.