function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}

addLoadEvent(function() {
  /* more code to run on page load */
  if (document.getElementById){
    // add extra functions to page tools list
    var print_page = document.getElementById('nav');
    // create print link
    var print_function = document.createElement('p');
    // print_function.setAttribute('class', 'print');
    //IE doesn't like this
    var print_function_link = document.createElement('a');
    print_function_link.onclick = function() { print_preview(); return false; }
    print_function_link.setAttribute('href', '#');
    var print_function_link_text = document.createTextNode('Print the Page');
    print_function_link.appendChild (print_function_link_text);
    print_function.appendChild (print_function_link);
    print_page.appendChild(print_function);
  }
});

function print_preview() {
  // Switch the stylesheet
  setActiveStyleSheet('Print Preview');
  // Create preview message
  add_preview_message();
  // Print the page
  window.print();
}

function add_preview_message(){
  var main_content = document.getElementById('content');
  var main_body = main_content.parentNode;
  if (document.getElementById){
    var preview_message = document.createElement('div');
    preview_message.id = 'preview-message';

    // Create Heading
    var preview_header = document.createElement('h3');
    var preview_header_text = document.createTextNode('This is a print preview of this page');
    preview_header.appendChild(preview_header_text);

    // Create paragraph
    var preview_para = document.createElement('p');
    var preview_para_text = document.createTextNode('Without this message of course. ');
    var cancel_function_link = document.createElement('a');
    cancel_function_link.onclick = function() { cancel_print_preview(); return false; };
    cancel_function_link.setAttribute('href', '#');
    var cancel_function_link_text = document.createTextNode('Return to the existing page.');
    cancel_function_link.appendChild(cancel_function_link_text);
    preview_para.appendChild(preview_para_text); 
    preview_para.appendChild(cancel_function_link);

    // Put it all together
    preview_message.appendChild(preview_header);
    preview_message.appendChild(preview_para);
    main_body.insertBefore(preview_message, main_content);
  }
}

function cancel_print_preview() {
  // Destroy the preview message
  var print_preview = document.getElementById('preview-message');
  var main_body = print_preview.parentNode;
  main_body.removeChild(print_preview);
  // Switch back stylesheet
  setActiveStyleSheet('default');
}