Here's my issue:
I had an HTML file and an external CSS file, both successfully linked. Changes I made in the CSS file were reflected on the website until suddenly they weren't. I tried commenting out code, refreshing the page, restarting the server and browser - but nothing worked. Even with everything commented out in the CSS file, the website continued to display the styles. It wasn't until after multiple restarts that my changes finally appeared. This isn't the first time this has happened and I'm curious if anyone knows what might be causing it.