It shows up on the menu but when I click on it nothing happens.
TIA,
Mike

Hiya Mike,

What is HTML 5 that you are trying to open VSD with? That's a very confusing question as you don't open VSD in HTML 5 so if you can clarify what you mean that might help us help you better

The Doctype options within VSD are transitional and strict – it doesn't specify what though. It used to have HTML 4 point something, in there.
Where do you see an HTML5 option?

I'm with JoAnn, a little confusing on the meaning of your question. A VSD page isn't going to validate or render correctly if you alter the page doc type with an outside source. Things VSD are better left to VSD to handle.