The problem:
You have a channel with lots of fields. You’ve spent ages making a beautiful custom publish layout for your client to make their life easy. You’ve separated your fields across multiple tabs and everything looks great. Your client then creates a new entry and leaves a required field empty. EE captures the error and adds a warning, but the field is on the second tab and the client can’t see it. They have no way of knowing there is a problem; they don’t even know the entry hasn’t been saved.
The solution:
Mega Error from Electric Putty is a free Expressionengine Accessory available for EE2.x which will look across all tabs within a publish layout for errors and flag them up in a way no one will miss.
For more information (And screenshots!) and to download go to http://labs.electricputty.co.uk/post/mega_error/