function openPopup(popup_width,popup_height,popup_url,var_name){
	var windowHeight = popup_height;
	var windowWidth = popup_width;
	var windowName = var_name;
	var windowUri = popup_url;
	var newwindow;

	var centerWidth = (window.screen.width - windowWidth) / 2;
	var centerHeight = (window.screen.height - windowHeight) / 2;

	if ( !newwindow || newwindow.closed ){
		newwindow = window.open(windowUri, windowName,'addressbar=0,menubar=0,location=0,status=0,scrollbars=yes,resizable=0,width=' + windowWidth + ',height=' + windowHeight +',left=' + centerWidth + ',top=' + centerHeight);
	}
	else  if ( newwindow && ! newwindow.closed ){
		newwindow.location = windowUri;
		// newwindow.focus();
	}
}