Can anyone tell me why this won't go through?
It won't go through because you have put your new CSS rule in with your HTML code instead of putting in the main.css file.
You can read more about that over here:
Thanks so much for your speedy reply, much appreciated! After reading your reply, I read through the instructions again and saw what I missed. I reset the code and went to the main.css file and tried it again there and it worked. Thanks again!