If you see horizontal scroll on your site it means some elements boxes are overflowing (go beyon viewport borders).

To find it open browser console and execute:

var docWidth = document.documentElement.offsetWidth;

[].forEach.call(
  document.querySelectorAll('*'),
  function(el) {
    if (el.offsetWidth > docWidth) {
      console.log(el);
    }
  }
);