Accessibility, WAI-ARIA Roles

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.

• application
• banner
• complementary
• contentinfo
• form
• main
• navigation
• search

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.

• combobox
• grid
• listbox
• menu
• menubar
• radiogroup
• tablist
• tree
• treegrid

References:
http://www.w3.org/TR/wai-aria/
http://www.w3.org/TR/wai-aria/roles