function alertSize() {
  var myWidth = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    myWidth = window.innerWidth;

  } else if( document.documentElement && ( document.documentElement.clientWidth) ) {
    //IE 6+ in 'standards compliant mode'
    myWidth = document.documentElement.clientWidth;
	
  } else if( document.body && ( document.body.clientWidth ) ) {
    //IE 4 compatible
    myWidth = document.body.clientWidth;
	
  }
  
  if(myWidth < 1200 && myWidth > 900){
	 document.getElementById('left_papers').style.display = 'block'
	 document.getElementById('left_papers').style.left = '-100px'
  }else if(myWidth >= 1200){
	 document.getElementById('left_papers').style.display = 'block';
	 document.getElementById('left_papers').style.left = '0px'
  }else{
 	 document.getElementById('left_papers').style.display = 'none';
  }

}

window.onresize = alertSize;