Additions to HTML standard

* More general rules
* Dropped "support" for <IE7
* Added lang tag to prevent having to add it for html5 validity
* Added utf-8 rule
* Added some information about semantics
Also the note on whatwg.org says:
>A character encoding declaration is required (either in the Content-Type metadata or explicitly in the file) even if the encoding is US-ASCII, because a character encoding is needed to process non-ASCII characters entered by the user in forms, in URLs generated by scripts, and so forth.