How do I undo changes to a page or revert to an older version?
Select the History menu item. Then select the versions of the page you wish to compare. When you find the version of the page you want to revert to, click on the edit link above the version you want. It will warn you that you are not editing the current version of the page. This is ok. Save the desired older version of the page. When you save the page, the older version will become the current version.
