When you login into a web site with user name and password, you sometimes have the option to store the password in your computer. This javascript when entered onto that website will reveal the password stored behind the asterisks (****) in the web pages of almost any web browser.
This code
This script can be useful if you have forgotten the password that you had saved on any website some time back. But does more harm than good if its in the wrong hands. I should know as I have found out many passwords using this nifty script courtosy of Raymond CC.

