$(document).ready(function(){
  var fromTop = getClientHeight()/2;
  var startMargin = fromTop-159;
  var startMargin2 = fromTop;
  //var startMargin = Number($("#button-order").css("margin-top").replace("px", ""));
  //var startMargin2 = Number($("#button-price").css("margin-top").replace("px", ""));
  $("#button-order").css("margin-top", startMargin+"px");
  $("#button-price").css("margin-top", startMargin2+"px");
  
  $(window).scroll(function(){
     var scr = getBodyScrollTop() + startMargin;
	 var scr2 = getBodyScrollTop() + startMargin2;
	 $("#button-order").css("margin-top", scr+"px");
	 $("#button-price").css("margin-top", scr2+"px");
  });
  
});

 function getBodyScrollTop()  
 {  
     return self.pageYOffset || (document.documentElement && document.documentElement.scrollTop) || (document.body && document.body.scrollTop);  
 }  
 
 function getClientWidth()
{
  return document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientWidth:document.body.clientWidth;
}

function getBodyScrollLeft()
{
  return self.pageXOffset || (document.documentElement && document.documentElement.scrollLeft) || (document.body && document.body.scrollLeft);
}

function getClientHeight()
{
  return document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientHeight:document.body.clientHeight;
}