Another installation / site management tip:

There is a free server monitoring service at http://uptime.openacs.org/uptime/

This service requires a web page that returns "success" if the server is up.

I created a module to do this, as follows:

File drupal/modules/uptime_test/uptime_test.info:

name = "uptime_test"
description = "Causes http://yoursite.com/uptime-test to returns 'success' to the uptime test at http://uptime.openacs.org"

File drupal/modules/uptime_test/uptime_test.module:

<?php

// uptime_test.module

function uptime_test_menu($may_cache) {

  $items = array();
  global $user;

  if ($may_cache) {
    $items[] = array('path' => 'uptime-test', 'title' => t('uptime test'), 'callback' => 'uptime_test_page', 'access' => TRUE, 'type' => MENU_CALLBACK);
  }

  return $items;
}

function uptime_test_page($args = NULL) {

  drupal_set_title('Uptime Test');

  print 'success';

  exit();
}

?>

I then enabled the module, tested the URL http://mysite.com/uptime-test, then entered the URL into http://uptime.openacs.org. It now checks my server every 15 minutes and sends me an email if it's down.