Thanks to bug 489245 and bug 498920, we have been able to verify a theory that many people are hitting F1 by accident.

We set up separate target pages for people who arrived on support.mozilla.com by selecting Help > Firefox Help from the menu vs people who arrived there by pressing F1.

The results for September:

* For people using the Help menu, the bounce rate was 32.3%
* For people pressing F1, the bounce rate was 98.2%!

These results clearly show that the user does not intend to open the support website by pressing F1 -- it is reasonable to believe that the F1 keystroke was accidental, e.g. when the user was typing.

The keyboard shortcut F1 should be removed from Firefox.