function get_login_param (param)
{
   if (param == 'screen')
   {
      var width = (screen.width) ? screen.width : '';
      var height = (screen.height) ? screen.height : '';
      var scrcol = (screen.pixelDepth) ? screen.pixelDepth + ' Bit Farbtiefe' : '';
      document.form1.login_param.value = (width && height) ? screen.width + " x " + screen.height + " px<br>" + scrcol : '';
   }  
}  

get_login_param ('screen');