If you click edit next to choose a form, then select the group you want to edit, and click edit on that, you will be able to click on the set to change the validation error message for the set.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.