METHOD:  navigator::preference

The preference method allows a signed script to get and set certain Navigator preferences. These preferences, along with their possible values, are as follows:

autoupdate.enabled
This preference is used to enable SmartUpDate, and its value can be set to either true or false.

browser.enable_style_sheets
This preference is used to enable style sheet, and its value can be set to either true or false.

general.always_load_images
This preference is used to automatically load images, and its value can be set to either true or false.

javascript.enabled
This preference is used to enable JavaScript, and its value can be set to either true or false.

network.cookie.cookieBehavior
This preference is used to determine how the browser deals with cookies: if its value is set to 0, it accepts all cookies, if 1, it only accepts those cookies that get sent back to the originating server, and if it is set to 2, it'll disable cookies

network.cookie.warnAboutCookies
This preference is used to warn before accepting cookies, and its value can be set to either true or false.

security.enable_java
This preference is used to enable Java, and its value can be set to either true or false.

NOTES:

To read a preference requires a UniversalPreferencesRead privilege, while setting a preference requires a UniversalPreferencesWrite privilege.