I have a menu resource thread but figured that this topic was different enough to be separate.
Second resource stays visible but looses the fade effect.
My demo is called Smooth seen here . Use theme switcher.
I used the second resources css code and some of his images, but removed the fade so it was easy to see.
I included a multi level drop down, search and page top-bottom buttons to show how versatile this could be.
The css control of this menu is called fixed css positioning, resource .
When using this you must remember this quote from resource
Fixed positioned elements are removed from the normal flow. The document and other elements behave like the fixed positioned element does not exist.
The height of your fixed menu is not added to your content, content moves up as if its not there. If needed you must add to your content extra height.