margin top resizer

resizer.js

(function(){
  
  var marginSetter = function () {
    var h = ($(window).height()) / .2;
    $('#my-element').css("margin-top": h);
  };

  // to run when the window is resized
  $(window).on('resize', function() {
    marginSetter();
  })
  
  // to load when the page loads
  window.onload = function() {
    marginSetter();
  };
})();