You can if you run Chrome. They just released an extension to do just this. (someone posted this on HN recently) http://googleblog.blogspot.com/2011/02/new-ch

You can if you run Chrome. They just released an extension to do just this. (someone posted this on HN recently) http://googleblog.blogspot.com/2011/02/new-chrome-extension-block-sites-from.html http://googleblog.blogspot.com/2011/02/new-chrome-extension-...