Expand this tutorial based on confused areas last night.

There were a couple of typos in this tutorial, as well as some parts
which tripped up the students I worked with last night. I've cleaned
those typos up, added some explanations for confusing bits, removed some
technical language in favour of plain English, and simplified some other
sections.
Merge pull request #127 from creature/gh-pages

Expand the HTML 1 tutorial based on confused areas last night.