Understanding and Using WordPress Autosave and Revision Features
Channel: buildwebsites
Date: 2011-02-13

http://www.buildingwordpresswebsites.com- An overview of the Autosave and revision  features and how they are used. Showing how to recover a previous page/post and how to revert back to an autosaved version of a post/page.
You are allowed 25 revisions which are created when you manually save/update a page or post but only one autsave. 
While you are editing a page/post any changed are automatically save every minute each autosave overwrites the previous one.
If you have browser crash or loose connection to the wordpress server or just forget to save your edits then the autosave feature can be used to restore your edits.
You cannot turn the features off they are present and enabled by default.