Facebook Keyboard Navigation: Browse Facebook with Keyboard Strokes
Regular Facebook users can use the Facebook Keyboard Navigation user script to quickly navigate around Facebook using the keyboard. Keyboard shortcuts generally speed up common browsing operations — just like in this case, so you’ll find it quicker to hit “I” to jump into your Facebook Inbox, “M” to send a message, “T” to get to the Facebook Notifications page, or “H” to go to your Home page. For more keyboard shortcuts move to the userscript web page. Keystrokes are case insensitive.
To use this script on Firefox you need to have the Greasemonkey add-on installed. With the Opera browser try this.