Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.
One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.
It is not possible to changes the default confirm button in javascript.
Instead i suggestion you can used your custom confirm box.
Below link will help you in custom confirm box.
http://www.codingforums.com/showthread.php?t=2581
Hope this will solve your problem.