Why does partial HTML 5 support matter?

[Perceptes]

With all the talk about HTML 5 support in Firefox and Safari lately, I have been wondering why it matters in any realistic sense. I haven't read anything directly addressing this issue. I've seen comments saying that you can now use certain HTML 5 features, but I don't understand how you can incorporate features of one specification into another. If I have a a document with an XHTML 1.0 doctype, isn't it invalid to use an element not defined in XHTML 1.0? Would using something like the audio or video tag just be relying on the user's browser to know how to interpret these mixed doctypes?

Another angle on this question is: Why does HTML 5 support in newer browsers matter unless IE has the same support? Web developers will always be limited by the weakest link (such as sites still essentially requiring compatibility testing for the ancient IE 6, though things are improving in this area recently). So is there any real value in some browsers supporting HTML 5 until all of them do? Modern browsers supporting HTML 5 doesn't realistically get us any closer to being able to use a real HTML 5 doctype. It all rests on IE. Is there a cause for excitement over this that I'm missing? Or is it just that people are happy to see things "moving in the right direction" in a general way?

 

[angelwatt]

Browsers are generally pretty relaxed on enforcing DOCTYPEs because let's face it, there's so many malformed web sites out there. If browsers complained too much about people having malformed HTML (whether from sloppy syntax or using tags from other DOCTYPEs) then 80%+ of the web would disappear.

Transitioning XHTML 1.0 to HTML5 will be an easy move, just change the DOCTYPE and you're done. HTML5 will be XHTML syntax ready through XML serialization. People are currently using tags like the video tag outside of the valid DOCTYPE, but it's a current necessity. While creators should try to validate their HTML, it's OK for it not to validate if they understand why it's not validating.

I don't use any HTML5 myself, but I can understand some people getting into it. With more people trying it out and putting it out in the open, it helps force companies like Microsoft to catch up and start implementing the new tags. Most people are just trying it out for fun and seeing what tomorrow has to offer. The same thing goes with all of Safari's (Webkit's) extra CSS implementations like CSS animations.

That's my take.