This week's book giveaway is in the Java 9 forum. We're giving away four copies of Java 9 Modularity: Patterns and Practices for Developing Maintainable Applications and have Sander Mak & Paul Bakker on-line! See this thread for details.
I don't know what "hitting submit" means in the context of your application. But it is probably connecting to a URL for which the relative pathactually points to your CSS file, and your original URL does not do that.