What are pros and cons, If I choose HTML 5 for all new projects?

Everyone, every blog is talking about HTML 5 and giving solution to use HTML in all b开发者_如何学编程rowsers including IE6.

• Should we leave XHTML 1.0 now and go for HTML 5 and use JavaScript for IE6 support?
• Does all other desktop/mobile browser except IE6 supports HTML 5 without adding JavaScript?
• Will every browser render CSS written for HTML 5 elements?
• What about Screen- readers?

What are pros and cons to choose HTML 5 for all new projects?

Pros:

• It has some nice new features

Cons:

• Support for those features is very thin on the ground
• QA tools are immature compared to those for XHTML and HTML 4.x
• The spec is still changing

Should we leave XHTML 1.0 now and go for HTML 5

I wouldn't. I'd stick to HTML 4.01.

and use JavaScript for IE6 support?

You need JS shims for more than IE6. I think IE8 might still require them - and that's for basic support for things like <article> just so you can apply CSS. Forget about <video> for the new form stuff.

Does all other desktop/mobile browser except IE6 supports HTML 5 without adding JavaScript?

No

A quick test shows that IE8 and Firefox 3.6 don't support <article> (IE8 doesn't appear to make it available for styling, Firefox styles it as display: inline by default)

Will every browser render CSS written for HTML 5 elements?

Not without JS hacks.

What about Screen- readers?

Most will not be able to do anything useful with the new elements

See also http://html5doctor.com/how-to-use-html5-in-your-client-work-right-now/

XHTML works with the HTML5 doctype and you need to change nothing as long as you are serving it as application/xml+xhtml and are using the HTML5 doctype.