Want to clear any stored information about one web site in particular, without clearing out all of your browser’s history files? Hidden deep within the Firefox browser, there is a way to clear Firefox’s history for just one single web site. You just have to know where to look.
From the Firefox menu bar, click on History and then Show All History. This should pull up the Library window. Now, in the Library’s search box (located in the top-right corner) type in the name of the web site you want to forget.
Scroll through your results, till you find the web site you wish to forget and select it. Now, right-click on the entry and click, “Forget About This Site”. All history items (browsing and download history, cookies, cache, active logins, passwords, saved form data, exceptions for cookies, images, pop-ups) will be removed only for that site. So be careful with using this choice and only use it if you really want Firefox to forget everything.
Now your browser history is cleared of that one annoying web site.