function getHeight() {
  var myWidth = 0, myHeight = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    myHeight = window.innerHeight;
  } else if( document.documentElement &&
      document.documentElement.clientHeight ) {
    //IE 6+ in 'standards compliant mode'
    myHeight = document.documentElement.clientHeight;
  } else if( document.body && document.body.clientHeight ) {
    //IE 4 compatible
    myHeight = document.body.clientHeight;
  }
  return(myHeight);
}

function ShowOffsetBox(element) {
	box = document.getElementById("offset");
	if (element.value <0) {
		box.setAttribute('style', 'display: inline');
	} else {
		box.setAttribute('style', 'display: none');
	}
}