Opentip

The opentip-class is a free opensource Java-Script tooltip class based on the prototype framework.

It supports:

Stems (little pointers)
Automatic content download with AJAX
Different styles
Automatic repositioning of the tooltip if it's not in the viewport of the browser anymore
All kind of triggers (The tooltip can be triggered by mouse over, click, form submit, … everything you can think of really)

Usage

<div onmouseover="javascript:Tips.add(this, event, 'Content', { options });"></div>

Or the preferred external method:

$('elementId').addTip('Content', { options });

For the complete documentation please visit www.opentip.org.

Opentip is written by Matthias Loitsch.
All graphics by Tjandra Mayerhold.