function newwindow(url,windowname, width, height, resize) {
	var parameters = ""
	if (width  != null) {parameters += "width=" + width + ",left=" + (screen.availWidth/2 - width/2) + ","}
	if (height != null) {parameters += "height=" + height + ",top=" + (screen.availHeight/2 - height/2) + "," }
	parameters += "scrollbars=no, status=0, ";
	if (resize != null) {parameters += "resizable=yes,"}
	var popupwin=window.open (url,windowname,parameters);
	popupwin.focus();
}