CSS :active selector

So I'm creating a basic website for myself, but I can't seem to get the CSS :active selector to work. Below is my code, and here is what I've tired. I've added a "active" class to the the li a link, used the same class name for the ul group and added :active at the end, etc. Could some please tell me what I'm doing wrong?

Sorry I didn't type the code here. I kept getting a coding format error. I didn't know what to do.

html code

css code