Michelle Barker wrote this nifty piece about blockquotes but then at the end talks about why it’s so important to learn HTML:
Conversely, it’s pretty easy to write bad HTML, because for most developers there are no consequences. If you write some bad Javascript, your application will probably crash and you or your users will get a horrible error message. It’s like a flashing light above your head telling the world you’ve done something bad. At the very least you’ll feel like a prize chump. HTML fails silently. Write bad HTML and maybe it means someone who doesn’t browse the web in exactly the same way as you do doesn’t get access to the information they need. But maybe you still get your pay rise and bonus.