Set up validation rules to prevent user from saving in Page Editor Mode using Sitecore

I recently encountered a scenario that in page editor mode, the client want to prevent content user from saving when the validation rules breaks which is not a default behavior. Here is how we can easily achieve it in sitecore.

Only CriticalError and FatalError will give your the pop up to tell you something is not right in page editor mode. The difference is FatalError will prevent you from saving and CriticalError will not but only with pop up warning message.

It is very easy to set up!