I can not see a setting that does this in HTMLEditor, but have you tried changing the Document Type? Although i don't think that is going to solve this issue.
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.