$(document).ready(function() {
  var ran = getRandomHeight('parentwrappper', 369);
  $("#parentwrappper").css({
  "margin-top" : "-" + ran + "px"
  });
  changeTestimonial('parentwrappper', 369);
  
  
  
 });
  
function changeTestimonial(parentwrapper, divHeight ) {
   var ran = getRandomHeight(parentwrapper, divHeight);
     
   var marginContent = "-" + ran + "px";
   $("#parentwrappper").animate({ 
      marginTop: marginContent
   }, 1500 );
   setTimeout( function(){ changeTestimonial(parentwrapper, divHeight); }, 5000);
}
 
 
function getRandomHeight(parentwrapper, divHeight ) {
    var totalDivs = $("#parentwrappper > .testimonialsBox").length;
    var maxPosition = (totalDivs * divHeight) - divHeight;
    
    var ar = new Array();
    var max = 0;
    while(maxPosition >= max ) {
         ar.push( max );
         max = max + divHeight;
    }
    var l = ar.length;
    var rnd_no = Math.floor(l*Math.random());
    return ar[rnd_no];
}