Javascript Countdown Timer

I need a countdown timer written in Javascript that will count down from a specified time (which we can edit in the code)? to zero (ie 9:00:00 to 0:00:00) and display the resulting? countdown realtime in the? users browser.? We'd like to be able to edit the style of the output, so please keep this in mind. The output format should be HH:MM:SS . The timer needs to be constant, despite refresh or reloads of the browser, this means we'd like it to use cookies as well. Once it reaches zero, we would like the display to show 0:00:00. The script should be self contained and make no other loads or calls outside of the page that it resides in.