Have you notice that Firefox 2 has some changes in ACCESSKEY and keybinding (keyboard) behaviour? They've changed some specific UI access key defaults to address some problems (with browsers/devices' UI chrome access keys) reported before. Try it with your web site and observe ALT + accesskey will not work anymore.
Some blogs said that you have to press ALT + SHIFT + Accesskey as the new default keyboard function for web content access. I searched some info about this at mozilla knowledge base, and found out some...changes... Anyway, try this.. to change this back to ALT + Accesskey again:
For your example, this website uses Accesskey -> C to go directly to our Contact Us page. Please press "ALT + C" to see if it works. No need to press the Enter key.
According to others, this gives the user/s the option to edit/customize their own keyboard functions for a specific browser.
For more specific info, possible values and their effects, check this out:
http://kb.mozillazine.org/Ui.key.generalAccessKey
http://kb.mozillazine.org/Ui.key.chromeAccess
http://kb.mozillazine.org/Ui.key.contentAccess
Update on FireFox 3.0
This instruction also works in the latest version of FireFox. The only difference is that you will see a prior warning screen saying:
This might void your warranty!
Simply click on the "I'll be careful. I promise!" button and off you go.