Why is it "teach your girlfriend"? Why does he presume that his audience has a girlfriend who needs to be taught, rather than a boyfriend? You can't say "well he has a girlfriend so he wrote it like that" because he's not talking about him in the title, he's talking about you - he's presuming you have a girlfriend who needs to be taught, and that's sexist. I don't think it's the crime of the century, but I do think less of the guy.
Then why does he say "teach your girlfriend" rather than teach your partner, or teach your friend, or teach someone? If the fact that it is his girlfriend is just his situation, why suggest that I teach my girlfriend in the title?
The internet is the world-wide network of computers. The web is HTTP and HTML and other such technologies, that may or may not run on top of the internet, but when they do they form the world-wide-web or web for short.
When people talk about clothes on the web, it's nonsense because they probably don't run HTTP.
Imagine if it said "how to teach your black friend to program". Why only black friends? Why only girlfriends?