window.onload = function() {

  // Hook up the contextmenu event on the container, not

  // on each list:

  hookEvent(document.getElementById('list_container'),

            'contextmenu',

            handleListContextMenu);

  // Our handler function

  function handleListContextMenu(event) {

    var target;

    // Handle IE-vs-the-world difference

    event = event || window.event;

    // Find out what the actual target element clicked was

    target = event.target || event.srcElement;

    // See if it or an ancestor of it is one of our lists

    while (target &&

           (target.tagName !== "UL" || !target.id || target.id.substring(0, 5) !== "list_")) {

      target = target.parentNode;

    }

    // Did we find a list?

    if (target) {

      // Yes, handle this.

      if (event.preventDefault) {

        event.preventDefault();

      }

      display("List '" + target.id + "' context menu");

      return false;

    }

  }

  function hookEvent(element, event, handler) {

    if (element.addEventListener) {

      element.addEventListener( event, handler, false);

    }

    else if (element.attachEvent) {

      element.attachEvent('on' + event, handler);

    }

    else {

      element['on' + event] = handler;

    }

  }

  function display(msg) {

    var p = document.createElement('p');

    p.innerHTML = msg;

    document.body.appendChild(p);

  }

};