function contentPosition(){
 if (typeof document.body.style.maxHeight != "undefined") {
  if(GetHeight()>=document.getElementById('mainContent').clientHeight){
    var contentPositionTop = Math.round(((GetHeight()/2)-(document.getElementById('mainContent').clientHeight/2))*0.8);
    document.getElementById('mainContent').style.position="fixed";
    document.getElementById('mainContent').style.top=contentPositionTop+"px";
  }
 }
}


function GetWidth(){
  var x = 0;
  if (self.innerHeight){
    x = self.innerWidth;
  }
  else if (document.documentElement && document.documentElement.clientHeight){
    x = document.documentElement.clientWidth;
  }
  else if (document.body){
    x = document.body.clientWidth;
  }
  return x;
}

function GetHeight(){
  var y = 0;
  if (self.innerHeight){
    y = self.innerHeight;
  }
  else if (document.documentElement && document.documentElement.clientHeight){
    y = document.documentElement.clientHeight;
  }
  else if (document.body){
    y = document.body.clientHeight;
  }
  return y;
}