TL;DR at bottom.
Short background: I'm a trainee Tech Support. Only have knowledge of HTML and currently training in the others. For security reasons I'd rather not link the website I'm working on.
Anyway, a client came in the shop and stated their website had been hacked and asked us to look into it. Sure enough it had been. I've managed to essentially get rid of all the crap they put on to the site and reverted it back to normal. That was the easy part.