Minor typo edits, few bits of explanation for new terms
Add some links to Mozilla's HTML & CSS reference pages, as extended reading material if people want to look into the details.

(I don't know of any better reference pages, feel free to enlighten me!)
Rework the forms example to remove gender binary option

There are some arguments to be made that requiring gender on web forms
is usually unnecessary, and also that asking for it as a simple binary
can be exclusionary. I know this is just an example form, taken from
Wikipedia, but it irked me a bit so I rewrote it as a pizza shop
order.
Add a few more notes about Dictionaries and their usage

I don't know if this is too much to introduce at once, but I think these are a few useful things to know before writing code with dictionaries.
Address @Ivoz's comments from 82b9bfa3019173533
Merge pull request #5 from projectgus/gh-pages

Few edits