YUITip is a simple YUI-based JavaScript that allows for a nice tooltip on any element that has a class of "tip" (the tip will pop up with the title of the element, so the element should also have a title attribute). You can optionally apply the script to work for all links by changing one flag at the top of the JavaScript file. If you like this you might also like my Pure CSS Tooltips (with optional CSS3 properties too!).
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