This method allows user script authors to persist simple values.
Strings, booleans, and integers are currently the only allowed data types.
Values are saved in the Firefox preferences back end and can be manually inspected or changed by typing about:config in the address bar and searching for the preference name "
(For appropriate values of
The Firefox preference store is not designed for storing large amounts of data. There are no hard limits, but very large amounts of data may cause Firefox to consume more memory and/or run more slowly. 
Compatibility: Greasemonkey 0.3b+
function GM_setValue( name, value )
BooleanAny valid value of these types. Any other type may cause undefined behavior, including crashes.