Add error message to top of page

Hi all.

Any pointers on how to display an error message for an incorrectly filled form, near the top of a page? Specifically, I'm looking to put a "there was a problem with your submission" message under the head of the contact page or at the top of the form. I'm sure the solution is simple, but I haven't come across it any searches, and my flu-addled brain just won't co-operate with me today.

I'm using OC 2.1.