What is the best way to make a <div>
fade away after a given amount of time (without using some of the JavaScript libraries available).
I'm looking for a very lightweight solution not requiring a huge JavaScript library to be sent to the browser.
Not sure why you'd be so against using something like jQuery, which would make accomplishing this effect all but trivial, but essentially, you need to wrap a series of changes to the -moz-opacity, opacity, and filter:alpha CSS rules in a setTimeout().
Or, use jQuery, and wrap a fadeOut() call in setTimeout. Your choice.