$(document).ready(function() {
  var height = $("#page-header").height()
  $("a").click(function(e) {
      e.preventDefault();
      var href = $(this).attr("href");
       $('html, body').animate({
        scrollTop: $(href).offset().top - height
       }, 0);
  });
});

$(document).ready(function() {
  var height = $("#page-header").height()
  $("a.internal").click(function(e) {
      e.preventDefault();
      var href = $(this).attr("href");
       $('html, body').animate({
        scrollTop: $(href).offset().top - height
       }, 0);
  });
});

Make the selector more restrictive
Make the selector more restrictive
