How do I learn in the "try it now" if the code is already written?

Question

Html coding

Answer 1

In programming a programmer must to know that
A. If code working, why?
B. Otherwise if not working, why?
Keep changing the code and see the difference of output.

Answer 2

In your programming path you will encounter a lot of code already written. A good way to learn from it is, read it, understand it, write down what you dont understand and search for the explanation on google. When you understand it try writing it on your own, also try to learn from good quality code and read style guides so you dont pick up any smelly habits. Good luck!