Please view this test of CSS3 background-size in Safari 3.
Tested in Opera 9.50 but the image stop/begin at around 15px from the left on the horizontal axis. The vertical axis is not rendered correctly since the height of each background is somehwhat keeping with the aspect ratio of the original image.
background: url(backblue4.png)50% 50%;-webkit-background-size:80% 80%