Turning Seconds Into Time Display In Countdown?

I am having a problem trying find out how to turn a number of seconds into a 00:00 format to do a countdown, and when it reaches 0:00 to redirect the window...

here is what I have figured out:

Code:

var tID = 0;
var startTime = null;
var timeout = 5*(60*1000);

[Code]....

Also, if they click the Button that says, "I'm still here" to ping the server to keep them on the page working without logging them out, will that code cause a javascript error because now the tooltip popup window that has the timeCountDown will no longer be open, so how would them clicking the ping server button stop that from causing an error when it goes to update timeCountDown?