function openWindow(url, width, height, features) {
  var scrHeight = window.screen.height;
	var scrWidth = window.screen.width;
	var left = Math.floor((scrWidth - width) / 2);
	var top = Math.floor((scrHeight - height) / 2);
  var position = 'left=' + left + ',top=' + top;
  var size = 'width=' + width + ',height=' + height;
  window.open(url,'contact', position + ',' + size + ',' + features);
}