BlockSite is a Firefox extension, which automagically blocks websites of your choice. Additionally, this extension will disable all hyperlinks to these websites, by just displaying the link text without the clicking functionality.

BlockSite should by no means be used for parental control or access control purposes, just because it isnt secure and can easily be disabled or even removed. BlockSite adds the site blocking functionality that was
removed from Adblock Plus.

You can add and/or remove websites, you dont want to visit ever again, via the BlockSite Preferences. You can open this window by clicking on the options button of BlockSite in Tools > Add-ons menu, or by clicking on the Preferences item in the context menu of the extension in the Extension Manager.
You can import and export lists of locations via the Import and Export buttons in the BlockSite Preferences window.

The first line in the file you want to import has to be the [BlockSite] in order to be read succesfully. So your file may look like:
If you lost your password: go to about:config (type about:config in the location bar and press enter) and reset the BlockSite.authenticate entry or clear the BlockSite.password entry.

The license of this software is Free, you can free download and free use this browser plug-ins software.