function open_window(fileName, windowName, windowWidth, windowHeight, scrollbars, resizable) {
	window.open(fileName, windowName, 'toolbar=no, location=no, directories=no, status=yes, menubar=no, scrollbars=' + scrollbars + ', resizable=' + resizable + ', left=' + centre(windowWidth, screen.availWidth) + ', top=' + centre(windowHeight, screen.availHeight) + ', width=' + windowWidth + ', height=' + windowHeight);
}

function centre(size,area) {
	return (area/2)-(size/2);
}