function dim_page(){
  // position code lifted from http://www.quirksmode.org/viewport/compatibility.html
  if (self.pageYOffset) { // all except Explorer
  var wt = self.pageYOffset;
  } else if (document.documentElement && document.documentElement.scrollTop) { // Explorer 6 Strict
    var wt = document.documentElement.scrollTop;
  } else if (document.body) { // all other Explorers
    var wt = document.body.scrollTop;
  }
 return(wt);
}