I assume you mean CSS3?
html5 is html 4.01 + xhtml 1.0 + new features (called “html5”).
so when you want a <nohtml5> you really are wishing for a <nohtml4.01> and <noxhtml1.0> also 
as for the how to serve video, that is already taken care of by html 4.01 or xhtml 1.0 <object> element. Raffles provided with with the solution: fallback option.
all in all, html5 wants to be a web Babylon, where all web’s html and xhtml be supported and more. that’s a plus.
but it’s also trying a vox populi approach, the cows path, trying to implement exceptions rather than standards. that’s a minus.
so html5 is trying too many fixes at one time to be successful any time soon. the hype has passed and now we see it was all a “i also want the 2010 web collection” transformed in “neh, it’s too funky” now. even the big guns that tried to push it forward admitted it will take longer until they will embrace html5.
and since html5 is still in draft, and many html5 feats are implemented in browsers in a proprietary way (-moz, -webkit), things can change radically until final specs get to us. and you need to remember it has to stick for it to become a day to day option. chances are it will not 
Great, thanks for all the help.
I still think I need a way to offer alternative content though. Thanks for the <video> one, but what about other HTML 5 tags?
http://www.breakingdownbaseball.com/ is a perfect example. View in a HTML 5 browser and looks good, view in IE 8 and doesn’t. How would they ensure the same site can be viewed on both (without producing 2 sites)?
John, here’s some information that should answer your questions/concerns: http://hsivonen.iki.fi/doctype/
http://crisp.tweakblogs.net/blog/434/using-the-html5-doctype-prematurely-considered-harmful.html
And these too:
http://www.alistapart.com/articles/a-brief-history-of-markup/
Thanks again to all.
I have decided to go fully HTML 4. For me, video and forms are the only thing that really interests me about HTML 5 (which the customer can appreciate anyway, I don’t think they care about semantic tags for example).
(I have a great rounded corners script that uses JavaScript).
For video I’ll use Flash and just serve .mp4 to devices that can’t use Flash (videos are free to distribute). (although I could use the method mentioned by Raffles for this)
For forms, then JavaScript (if at all needed) will do the job (date pop-up box etc).
Thanks again.
Regarding your “<nohtml5>” thing - <video> has a fallback option:
<video src="vid.flv">
<object>
...
</object>
</video>
The <object> will be ignored if HTML5’s <video> and the codec are supported. Otherwise, the <object> inside is displayed as a fallback option.
Ah. No, autofocus is only defined for form controls and only has an effect when the element is inserted into the document (which is typically by the parser). If you want to move focus to something in a widget or app based on some user action, use focus().
Ah ok. So,
“autofocus is a less-evil focus()” right?
For those apps where people use focus() to help people use some widget, autofocus was meant for this rather than for what google or mail.lycos.com do right?
given our further dialog, your comment should have been: “Eh? HTML has nothing to do with XHTML”
but html5 has all and more to do with xhtml 1.0 since developers can choose xhtml over html anytime they want when opting for the html5 DTD.
Frankly, I think it’s more trouble than it’s worth.
If your audience is one you want to impress with your HTML5 skillz, they probably won’t be using IE, so IE isn’t a major issue. Alternatively, if your main concern is cross-browser compatibility so that any visitor will see your site properly, then ditch HTML5 until it’s mature, and use good ol’ HTML 4.01 instead. There’s nothing wrong, old or out of date about HTML 4.01. It’s currently the best thing out there.
You can’t use html5 elements and have support in IE6-IE8 without scripting, which is never a good idea.
But if you must:
There are other scripts.
If you want to go all the way and still support IE (requires JS eanbled), this will demonstrate what it takes to accomplish that (and you’ll still not support anyone on a legacy browser outside IE and only the IE users with JS enabled): http://html5boilerplate.com/
No, there isn’t such a thing.
That is correct, you cannot use HTML5 if you want cross-browser and legacy browser support. Even if you use Javascript to emulate HTML5 elements in IE, you’ll have IE users without JS alienated. You’ll also have any and all users who use significantly older versions of Webkit or Mozilla browsers without luck.
Like Raffles said, if you have a site where you can go crazy with experimenting, e.g. a site by designers for designers, some personal blog or similar, nothing wrong with trying it! If you cater to a mixed audience, I’d stay away from going that drastic route just yet.
In any case, there’s nothing wrong with learning HTML5.