Most of the changes made in a site are logged in a file which can be downloaded in a CSV format. Information such as who edited the site, or when, can be found in this log.
These logs can be a good reference to decide which published version you'd want to restore the site, since these logs are listed chronologically.
To download the log file:
1. Click the site from the Site and Templates dashboard.
2. Click More from the Site Details menu.
3. Click Edit History button.