Using the accesskey attribute, you can enable hotkeys for various html input elements. This allows one to get the focus to an input element by using the ALT-key + <CHARACTER> (on Windows) or CTRL-key + <CHARACTER> (on Mac). This way, your page is accessible by keyboards besides mouse.
Here's the example taken from the Mozilla DevCenter:
<label value="Enter Name" accesskey="e" control="myName"/> <textbox id="myName"/> <button label="Cancel" accesskey="n"/> <button label="Ok" accesskey="O"/>
Both buttons as well as the input box can be accessed by ALT+E, ALT+N, ALT+O on Windows or CTRL+E, CTRL+N or CTRL+O on a Apple-Mac.
This is quite easy to program, and works for all popular browsers (including Internet Explorer, Safari or Firefox).