About Locking Preferences
Preferences can be locked at any level above the individual user. If a preference is locked, then the locked icon 
displays next to that preference at all levels, and the preference value cannot be changed at lower levels.
displays next to that preference at all levels, and the preference value cannot be changed at lower levels.For example, if a site administrator locks a particular preference at the site level, then that preference cannot be changed by the organization administrator, any application context administrator, or a user. If an organization administrator locks a particular preference at the organization level, then that preference cannot be changed by the administrator of any application contexts, such as a product or project, within that organization.
 | Before locking a preference value at the site or organization level, it is recommended that you delete any existing child instances for that preference. |
Locked preferences can later be unlocked.