If you're having trouble getting Deliguy's javascript book mark to work take a look at this image
I'm on OS X using a browser called Camino, which for all intents and purposes is the same as firefox. I had to copy his link and edit it a bit to get Camino to accept it as a bookmark.
You may notice that your browser tries to open http://javascript... or something similar when it should be executing some javascript.
Below is an image of the "cleaned up" javascript code that you can add as a new bookmark to your bookmark folder/bar.