Drupal Revision Control
Drupal allows you to revise your content and keep track of both the original version and all the revisions you make. Revisions may be the result of a mistake, leaving out some important bit of information. Maybe something new happened, making the current content inaccurate. Documentation of the revision may be as important as the making of the revision.
To create a revision, follow these steps:
Log in to your site as administrator.
Choose a basic page or article you created earlier and click the Edit link.
Make a change in your content.
Scroll down to the Revision Information link and click it.
Select the Create New Revision check box and type something in the Revision Log Message box that explains changes you have made to the content.
Your revision has been saved, and you will now see a new Revisions tab that you can click to see all saved revisions.
Next time you edit the content, you will see the current revision. If you want to edit the current revision but not create a new revision, don't use the revision settings when editing. To go back to the original version, click the Revert link on the Revisions tab.
Revisions are great for keeping track of changes to the content:
If you need to make a temporary change to content on your site but eventually want to go back to the original, you can create a revision and then click Revert when you no longer need the latest change.
When more than one person works on the same site, the Revisions feature can record when someone else changed something and why.