Canview

Chances are, canview (formerly viewall) is not a query string argument for you. You should not use it. All uses are logged. The list of members who have access to this privilege is not public; however, it should be noted that only certain LiveJournal/Six Apart employees have this privilege. It has different arguments, such as "suspended", which allows the person with the privilege to view public posts in a suspended journal.

No argument will allow the user to see entries regardless of their security.

Some people have accused the abuse team of abuse of the privilege. You can see whether or not the viewall privilege is being used to view your journal through the use of an image bug, as described in the previous post link.