Add Custom Tag to Visual Studio Validation

Question

How can I add rules to Visual Studio (2005 and up) for validating property markup (HTML) for a vendor\'s proprietary controls?

My client uses a control which require

Answer 1

Right-click on the Source view of an HTML / ASP page and select "Formatting and Validation".

1. Click "Tag Specific Options".
2. Expand "Client HTML Tags" and select the heading.
3. Click "New Tag...".
4. And just fill it in!

I wish that I could add custom CSS values as well.