Your answer compare needs a nl2br in its output, at mo it looks a mess.
I do not think this is any good at all. I thought you were going to parse my answer and see if it did what you asked it to do (CI general Q1 - write a controller to echo 'Hello World'.
To have a 'take a look at the answer and see if you were right' is pointless.
Perhaps you should try to make your quiz site a bit more fun, with multiple choice answers so you can easily check the answers.
Also your questions are input fields too, so my first attempt I wrote my answer in the question block.
So I am sorry, but no, at the moment your site is not a good idea, is not well thought out, and is not very well implemented.
It is also still very slow.
Paul.