// Show button on scroll
window.onscroll = function() { toggle_gototop() };

function toggle_gototop() {
  gototop_button = document.getElementById("gototop");
  if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {
    gototop_button.style.display = "block";
  } else {
    gototop_button.style.display = "none";
  }
}

function gototop() {
  document.body.scrollTop = 0; // For Safari
  document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
}