Rounded Corner <div> with background image

[Tux.Ice]

I would like to know how to do this:

I have this website: http://go-techo.com/ As you can see, the corners are rendered using javascript, but they have white pixels around them because the JS can't handle a background image. How can I replace the corner images with this image (http://go-techo.com/img/nav_corner_let.png) and the various rotations of it? I have tried a few tutorials on the net, but none of them seem to work, Help would be appreciated :D

[mssever]

I would like to know how to do this:

I have this website: http://go-techo.com/ As you can see, the corners are rendered using javascript, but they have white pixels around them because the JS can't handle a background image. How can I replace the corner images with this image (http://go-techo.com/img/nav_corner_let.png) and the various rotations of it? I have tried a few tutorials on the net, but none of them seem to work, Help would be appreciated :D
Browsers typically are bad at manipulating images. I suggest storing PNGs of the corners in the proper size and rotations and just linking to them. Trying to manipulate a single image with JavaScript is just borrowing trouble.

[Tux.Ice]

I'm not trying to manipulate it with the Javascript, I don't know how to link to it, and add rounded corners to a <div> that alreday has a background image.