HTML: What is this yellow equal sign? It prevents my code to function

Hi!

Wha is this yellow equal sign in my HTML code? This line doesn’t work in the browser but if I copy-paste this code and the css into CodePen, everything works.

Thank you!

Well, at least managed to fix my html/css issue by copypasting the css code into the .html between tags in … for some reason not all of my styles can be read from my stylesheet…weird. Couldn’t find any issues with my stylesheet, everything seemed right.

Also still don’t know the meaning of that yellow equal sign.