If you have made some changes to a page and want to revert to a previous version of your page you can do this by enabling the revisions in your pages or posts. Revisions of pages are not kept for long and are automatically flushed from the database every month.
To enable the revisions click on “Screen Options” when editing any of your posts and pages and put a tick in the revisions checkbox (this may already be enabled)
Edit the page you want to restore the revision for and scroll to the bottom of the page and you will see a revisions section listing all the changes that have been made and the date they were made, click on the date and time of the revision you want to restore
Now you will see the option to restore the revision and below that you will see the comparison in the current page and the one ylou are about to restore, click the “Restore This Revision” button to restore this version