var aryImages = new Array(4);
aryImages[0] = "/graphics/buttons/btncontinueon.jpg";
aryImages[1] = "/graphics/buttons/btncontinueoff.jpg";
aryImages[2] = "/graphics/buttons/btncancelon.jpg";
aryImages[3] = "/graphics/buttons/btncanceloff.jpg";

for (i=0; i < aryImages.length; i++) {
var preload = new Image();
preload.src = aryImages[i];
}