What is HTML5 ARIA

http://stackoverflow.com/questions/3474099/what-is-html5-aria

https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA

http://www.w3.org/TR/aria-in-html/

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问：What is the difference between data attribute and aria? 
答： aria is specifically for accessibility, and should not be used to store random data. data is for random data the application needs to associate with the node.

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ARIA stands for Accessible Rich Internet Applications.

WAI-ARIA is an incredibly powerful technology that allows developers to easily describe the purpose, state and other functionality of visually rich user interfaces - in a way that can be understood by Assistive Technology. WAI-ARIA has finally been integrated into the current working draft of the HTML 5 specification.

And if you are wondering what WAI-ARIA is, its the same thing.

Please note the terms WAI-ARIA and ARIA refer to the same thing. However, it is more correct to use WAI-ARIA to acknowledge its origins in WAI.

WAI = Web Accessibility Initiative

From the looks of it, ARIA is used for assistive technologies and mostly screen reading.

Most of your doubts will be cleared if you read this article

http://www.w3.org/TR/aria-in-html/

更新：详见： http://www.cnblogs.com/TomXu/archive/2012/01/05/2305453.html