I took the exact textarea code and tried it on a test page and the validation showed for me... it must be something else on the page causing the issue.
Do you have a url where I can see the problem?
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.