How to create a simple and browser independent tooltip?

I'm trying to create a tooltip like the one that youtube开发者_如何学Python shows you when you hover over their "like" button, for example.

How can I achieve this in a simple and browser compatible way?

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You're looking for a tooltip plugin. Try QTip2 (if you're using jQuery.)

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What you are referring too is a tooltip.

Most commonly is this effect initiated by JavaScript, a vast majority requiring the jQuery, Mootools or Prototype -javascript libraries. There are probably ways of doing this with CSS as well, but these will have many compatibility issues across browsers

this list shows a lot of these plug-ins: http://www.webdesignbooth.com/15-jquery-plugins-to-create-an-user-friendly-tooltip/