Hi Christiano,
Can you describe a bit what are you trying to accomplish? I believe there is some misunderstanding here, since the CSS provided does make your NavBar transparent but since the content element is below it and has overflow: hidden, it won't be visible under the NavBar when you scroll. Maybe you want all the scrolling content to pass under the NavBar? Then you need to remove the overflow: hidden from .km-content and move the background to the .km-scroll-container.
Regards,
Kamen Bundev
Telerik
Join us on our journey to create the world's most complete HTML 5 UI Framework -
download Kendo UI now!