query about cache memory

I use firefox as my default internet browser.It runs smoothly and fast.But The problem is everytime I visit a link or sublink it reminds it for ever.So when I start typing in the address bar it displays all old and new links with the letter or words and the list is long......
I heard the browser uses the cache memory which is a part of RAM.So can the saved links harm the speed of computer?
How can I delete them?Please help!!!
REGARDS:
mistu4u

That would be the history. You can delete from the browser tools or you can use a third party app like CCleaner.

http://www.piriform.com/ccleaner

This can take up some disk space, and can slow down the computer. I once had a friend that had 11GB of temporary Internet files.

Besides:
In FF,go to history and delete whatever you want......
You can also press Ctrl+Shift+H or Ctrl+Shift+Del(works also in IE) and delete.Have fun....

Go tools > options >privacy Then in the two boxes choose "never remember history" And location bar "nothing".