function setBottom () {

	if (window.innerHeight && window.scrollMaxY) {// Firefox
		yWithScroll = window.innerHeight + window.scrollMaxY;
		xWithScroll = window.innerWidth + window.scrollMaxX;
	} else { // works in Explorer 6 Strict, Mozilla (not FF) and Safari
		yWithScroll = document.body.offsetHeight;
		xWithScroll = document.body.offsetWidth;
  	}
  	
  	dim = getSize();
  	
  	// position 
  	var bottom = document.getElementById('bottom');
  	
  	if(yWithScroll>dim[1]) {
  		var y = 50;
  		
  	} else {
  		var y = (dim[1]-yWithScroll - 50);
  	
  	}
  
  	
  	bottom.style.marginTop = y + "px";
  	
  	
}


window.onload = setBottom;

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];
}