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
I look at `html` and `head` as a given otherwise we are not writing valid html. I will adjust the wording though.

The reason I put it in there is because during my validations of our own websites I came across a handful of websites that did not specify encoding properly. So, I wanted to put it in the standard as a reminder.