window.name="imagewindow";  
function OpenImageWindow(file, width, height)
{
var theTop = (screen.height/2) - (height/2);
var theLeft = (screen.width/2) - (width/2);
window.open(file, "ImageViewer", "top=" + theTop + ",left=" + theLeft + ",width=" + width + ",height=" + height + ",resizable=0,scrollbars=0,toolbar=0");
}