Floating navigation bars have become very popular on sites like Facebook and Google+. It is a great way for users to be able to move efficiently around your site.
Create a simple page structure with a header, content area, and footer.
Make sure that the body has no margin, otherwise the navigation bar will look awkward. Next, style the header div any way you like, then set the width to 100% and the position to fixed. A height will also need to be set for the next step.
Here is what the final product should look like.