CSS3 Background image question

I’m building a website in html5 and css3. I have several background images layered on top of each other. I’d like the image on the top layer to be centered horizontally, but have a specified vertical placement from the top of the page. Is this possible? I’ve looked up all I could find on css3 backgrounds and I saw that images could be centered or positioned in a way similar to absolute positioning. Is there a way to combine the two?

Thanks for your responses.

I works like this (not in code tags to highlight)
background-image: url(sheep.png), url(cow.png);
background-position: center center, left top;

This wil give you a sheep in the middle (center on x annd center on y) and a flying cow in the left top.

Thanks. That helped a lot!