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

function getHeight(element)
{
var myHeight = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    myHeight = element.clientHeight;
  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
    //IE 6+ in 'standards compliant mode'
    myHeight = element.offsetHeight;
}
  return myHeight;
}

function jumpToTheTopMain()
{
setTimeout(isScrollable,100);
}

function isScrollable() {
	scrollable = false;
	if(getSize()[1] < getHeight(document.getElementById('jump_to_top').parentNode))
		scrollable = true;
	
	if(scrollable)
	{
		document.getElementById('jump_to_top').style.display = 'block';
	}
}

addLoadEvent(jumpToTheTopMain);