function show_modal() {
  $(window).scrollTop(0);
  $("#modal, #lightbox").show();
  $("#lightbox").center({
    vertical: false,
    horizontal: true
  });
}

function hide_modal() {
  $("#modal").hide();
}

function modal_loading(show_text) {
  $(window).scrollTop(0);

  if (show_text == true) {
    $("#lightbox").html("<p style=\"text-align:center;\">Loading, please wait...<br/><br/><img src=\"../common/images/loading.gif\" /></p>").show();
  }
  else {
    $("#lightbox").hide();
  }

  $("#modal").show();
}