This plugin detects the edges of the browser window and will make sure the tooltip stays within the current window size. As a result the tooltip will adjust itself to be displayed above, below, to the left or to the right of the element with TipTip applied to it, depending on what is necessary to stay within the browser window.
TipTip is a very lightweight and intelligent custom tooltip jQuery plugin.
It uses ZERO images and is completely customizable via CSS. It's also only 3.5kb minified!