Javascript popup/lightbox script wanted

Please look at my site [login to view URL] You will see a popup window after a couple of seconds. While the content of the window and the operation of the form is OK, I feel that the popup action is rather clumsy. Here is a much better example that I found (not my site)? [login to view URL] Ignore the red bar at the top. The popup appears after around 10 seconds. I like the centering, the darkening of the background and the smoothness in the way it appears. I also like the way the background can be scrolled while the popup stays centered. I would like a similar script to power my popup. I need it to work in Explorer, Firefox, Chrome, Opera, and Safari, on Windows, Macintosh, iPad and other common devices. I would like the delay time to be adjustable, also the rate at which the popup brightens and the background darkens. It would also be nice to be able to set how dark the background is. Please only bid if you have done this kind of thing before and you KNOW what you are doing. I only need the script, which I can install myself. I don't need any HTML.