function getPageSize(){ 
  this.x = 0;
  this.y = 0;

  if(window.innerWidth && window.innerHeight) {
     this.x2 = window.innerWidth;
     this.y2 = window.innerHeight;
  }
  else {
    if (document.body.offsetWidth && document.body.offsetHeight) {
      this.x2 = document.body.offsetWidth-20;
      this.y2 = document.body.offsetHeight-5;
    }
    else {
      this.x2 = 0; this.y2 = 0;
    }
  }

  this.x50=this.x2/2;
  this.y50=this.y2/2;
  return this;
}