Let's say the height of the div is 34px and the width is 480px. The div should look like this:
and I don't want it to actually use an image, just CSS. Is it possible?
It is with CSS3. There's even a handy gradient generator which takes the guesswork out of it. Of course, this is completely unsupported in IE8 and under.
For the sake of completeness, as sluukkonen mentioned, IE does support gradients in CSS using the filter filter:progid:DXImageTransform.Microsoft.Gradient
.