Both the start and end tags of the head element are actually optional, user agents will automatically produce these if not present in the code. However, if you are coding with Extensible Hypertext Markup Language (XHTML) you will not pass validation due to an error.
The opening html tag when expanded with a few attributes is a real boon for increasing the accessibility of your web pages. In this the third article in my "From the Top" series, I'll introduce each of those attributes and explain the benefits of their use.
Content negotiation at its simplest is a conversation between your web server and a user agent (browser, search engine bot etc) to determine the preferred format or version of a resource to serve. In this, the second in my article series "From the Top" I will introduce you to the web (head) waiter that knows how to correctly serve your web page to a user agent.
