WAI-ARIA, the Accessible Rich Internet Applications Suite, defines a way to make Web content and Web applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with Ajax, HTML, JavaScript, and related technologies.
http://www.w3.org/WAI/intro/aria.php
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Landmark Roles – The following roles are regions of the page intended as navigational landmarks.
Widget Roles – The following roles act as standalone user interface widgets or as part of larger, composite widgets.
alert
alertdialog
button
checkbox
dialog
gridcell
link
log
marquee
menuitem
menuitemcheckbox
menuitemradio
option
progressbar
radio
scrollbar
slider
spinbutton
status
tab
tabpanel
textbox
timer
tooltip
treeitem
Widget Roles – The following roles act as composite user interface widgets. These roles typically act as containers that manage other, contained widgets.
References:
http://www.w3.org/TR/wai-aria/
http://www.w3.org/TR/wai-aria/roles