Access key
An access key allows a computer user to immediately jump to a specific part of a web page via the keyboard. In most web browsers, the user does this by pressing ALT (PC) or CTRL (Mac) followed by the appropriate character on the keyboard. In Opera, the user presses SHIFT-ESC followed by the access key (without ALT).
In the summer of 2002, a Canadian Web Accessibility consultancy did an informal survey to see if implementing accesskeys caused issues for users of adaptive technology, especially screen reading technology used by blind and low vision users. These users require numerous keyboard shortcuts to access web pages, as "pointing and clicking" a mouse is not an option for them. Sadly, their research showed that most key stroke combinations did in fact present a conflict for one or more of these technologies, and their final recommendation was to avoid using accesskeys altogether. (See the link below: Using Accesskeys - Is it worth it?)
The W3C, the organization responsible for establishing internet standards, has acknowledged this short-coming, and in their latest draft documents for a revised web authoring language (XHTML 2), they have deprecated (retired) the ACCESSKEY attribute in favor of the XHTML Role Access Module.
Specifying access keys
Access keys are specified using the accesskey attribute. The value of the accesskey attribute is what the user will press in order to follow that specific link. The accesskey attribute sets the value of the accesskey. For the below link you would press ALT+H (on a PC, Cmd+H on a Mac, Shift+Escape H on Opera) to be directed to index.php.
<a href="index.php" accesskey="h">Home</a>
Wikipedia access keys
See also the access keys used in Wikipedia: Wikipedia:Keyboard_shortcuts