...first, so this works for me now:

#CssName{
	background-image: none;
	background-color:green;
	color...

...Button btn = new Button("Test");
        btn.setName("CssName");

        string cssPath = dirName(wd) ~ "\\" ~ "test.css";

        CssProvider...

...Button btn = new Button("Test");
        btn.setName("CssName");

        string cssPath = "test.css";

        CssProvider provider = new...

...Button btn = new Button("Test");
        btn.setName("CssName");

        string cssPath = "test.css";

        CssProvider provider = new...