I've used this site before and I've got to say, I've enjoyed it. The good thing about it is that even if you don't know a thing about hacking, you should be able to find the solutions.
I do not agree with you to an extent. I believe that you have to at least have some background knowledge on HTML, javascript, programming, etc. in order to complete most of the missions on the website. The only mission where you probably do not need to have background knowledge on anything is looking for a password clearly marked in the source code.



