Found when I hit the back arrow and it would not go back a page. Checked the drop down menu and there it was.
If you are talking about the drop down menu for the browser's back/forward buttons.. That is not registery, that's browser history.. Simply closing the page will get rid of it.
However if you want to sweep the history clean CCLeaner will do the trick IT can also dump your cookie jar.
Now, if you want to never visit a web site (This my cause issues but is easily fixed)
In Windows | System32 | Drivers | Etc (This is for xp) there should be a file called simply HOSTS,, Not Hosts.txt or hosts.abc or anything with a dot extension just plain HOSTS
Open it for edit, NOTEPAD can do it just fine
There is a line in there
Local host 127.0.0.1 or
127.0.0.1 local host (Forget which)
Copy that line, only replace "Local host" with the site you want never to visit
IE: 127.0.0.1 googleheds.doubleclick.com