Access keys/Details of values
From Bjoern Hassler
From http://kb.mozillazine.org/Ui.key.contentAccess :
0 Disable the accelerator key for the content.
1 Use "Shift" for the content access key.
2 Use "Ctrl" for the content access key. (Default in OS X)
4 Use "Alt" for the content access key.
8 Use "Meta" for the content access key.
(Other) You can add any of the above values together to combine their functionality. That is, setting this preference to 3 (i.e., 1 + 2) means you need to press "Shift+Ctrl". In Windows and Linux, the default is 5 ("Shift+Alt").)