Every time you edit the content or change a property of a page, a new version is saved.
To view the saved versions of the current page, when logged in, go to the page for which you want to view older versions. On the Tools Menu, click "Versions" and you'll see links to your older versions of that page. You can also click the Versions tab when editing a page to view it's version history.
If you need to log in before having access to edit your site, you'll also need to log in before viewing the Versions page.
The Versions page contains a list of all saved versions of the current page. Each version is listed by Version Number, Revision Date, Title, the name of the User who made the version, and a comment, if one was entered.
You'll see a Diff link next to each page version. Click this link to see a side-by-side comparison of this version and the previous version. Lines are highlighted based on whether they were added, deleted, or modified. (You can also reach this report by clicking the Version number in the Recent Changes report for your site.) Click "Back" on the Diff screen to return to the Versions page.
Click a Version number to view that version. You can revert any page to a previous version by clicking the version number you want to revert to in the Other Versions page. Then click Edit This Page to bring the version into the Editor. You can make changes if you choose, then click the Save button. A new version will be created based on the content of the previous version. Versions created after the version you chose on the Other Versions page will still exist.
Page versions only contain copies of the text of the page, so they take up very little of your site's allocated disk space. However, hundreds of page versions can add up. Use the Disk Space & Bandwidth tool to monitor your disk usage. If space gets tight, you can delete old versions based on date. See Disk Space & Bandwidth in Site Settings for more information.