Look at jQueryUI. http://jqueryui.com/ But, keep in mind that some of those UI widgets like dialog, don't work well on mobile devices.

You'll use jQuery to help with the javascripting of things like "If this checkbox is selected, then enable these other controls" or even the AJAX/JSON data stuff..

>I understand, conceptually, what Javascript if about. But I need to go through an example to see how it works for UI. That is, aside from being able to process code on the client side, how JQuery helps to build "nicer" (for the lack of the term) UI.
>Thank you.