Html5 is under development, but you make it sound like it is still Alpha.
Originally Posted by webdev1958
There might be minor adjustments, but most changes are extensions to the language.
Html5 is now a reliable language.
Originally Posted by Jesper Møller
<meta last-modified="Thu, 14 Apr 2011 12:17:27 GMT" />
and the content for
<meta http-equiv="last-modified" content="Thu, 14 Apr 2011 12:17:27 GMT">
http-equiv="Expires" must be a date string just like the
but should be the date when the currently cached files should no longer be valid.
Though it can be used as an alternative no-cache, it is not its purpose.
It will still not be recognized as Valid by the validator, but it is to be ignored, as the validator is not fully up to date, as despribed under "Notes and potential Issues" on the validator page:
Using experimental feature: HTML5 Conformance Checker.
The validator checked your document with an experimental feature: HTML5 Conformance Checker. This feature has been made available for your convenience, but be aware that it may be unreliable, or not perfectly up to date with the latest development of some cutting-edge technologies. If you find any issues with this feature, please report them. Thank you.