Ideally one day I would like to be able to understand HTML and PHP.
And then! and then! and then! there are the joys of Apache so you can start twiddling with your .htaccess file and learn whole new ways to bring your site crashing to the ground. (Right now I am very thrilled because I managed to make an htaccess error that didn't shut down the site, it just prevented all images from displaying.)
The very nice thing about both html and css is that they're explicitly designed to be tolerant. You would have to make a HUGE mistake to have really visible consequences. Otherwise the browser just ignores that part it doesn't understand and carries on regardless-- this is in The Rules-- and your human users never know anything was amiss.