To completely unpublish a page, view the page and click the Unpublish this revision link.
Doing this will unpublish the LIVE version of the page, and users not logged in will see the following screen.
Only unpublish pages if they should not be publicly accessible any longer.
Reverting Page Changes
To revert the changes on a page, view the page and click the Moderate button.
Next, find the revision you would like to restore, and click the Revert link
Please note that blocks, subnav and navigational changes to a page will not show up in the moderation workflow and cannot be fixed through reverting page changes.