1. Where do you put your CSS files?

First to be able to use GWT Designer without the “There are no CSS files referenced from modules or HTML” error, you have to do this:

Second, to be able to use the css file during runtime, you have to reference it in your gsp page as well. Like this.

2. How come my create-gwt-page index.gsp does not work?

For some odd reason, index.gsp cannot be found, but if I renamed that to anything else, main.gsp or hello.gsp, it works.