TYPO3 preview without https

A typical scenario: Your TYPO3 backend is https encrypted but some of your frontend websites don't need encryption. So without any configuration you would have preview links from the backend using https without a matching certificate!

Just add this line to the root page of the domain in pageTS

TCEMAIN.previewDomain = http://my.domain.com/

Here you can define exactly what to show for any preview.