Complete list of reasons why a css file might not be working

Question

This problem is making me feel like an absolute noob.

Here is the head of my .html file:

Answer 1

I had a problem like this! I was able to fix it following

Step 1>>from Abraar Arique post, I went into the console>> Went under Style Editor and found Firefox wasn't loading the updated copy of my css file.

I cleared all history and reload the page then my problem was fixed.