I still recall, when I started using Role Tailored Client (RTC), that one of the things of that really surprised me was the error messages that appeared in the yellow ribbon.
Well, it was actually not the message as such, or the yellow ribbon, it was more the fact that the error did not prevent me from moving to another field. Although I did enter an invalid value I could just continue working on other fields. That was totally new to me as, on any error thrown, the good old classic client would block any successive action by a user unless it solved the error, e.g. change the value entered to a valid one.
This memory came to mind when I was reading this useful help topic on the differences between validation on Classic Client and RTC. In the context of my posts on Validating Data I would like to recommend this topic to you.