Removed Mac-specific links to wiki pages no longer maintained
[1] Level 1 restrictions are a subset of level 2. Level 2 restrictions are a subset of level 3.
See [https://wiki.mozilla.org/Sandbox/OS_X_Rule_Set#How_security.sandbox.content.level_Affects_File_Access How security.sandbox.content.level Affects File Access] and [https://wiki.mozilla.org/Sandbox/OS_X_Rule_Set Filter rules] for more details.
