How do I redirect to another URL when "This webpage is not found" URL is displayed

I am using gatekeeper for simple security for a web page but if the user keys in the wrong password (which is the file name), they are directed to a URL that doesn't exist (because it's not the right file name). I would like to know if there is a way in javascript to redirect to another web page instead.

The code for gatekeeper can be found at:
http://www.htmliseasy.com/keeper/index.html

 

Perhaps using ajax to check file existence before form submission
could be the solution.

Hendra

 

Use htaccess to redirect