How to restrict access to the site during development?
Make a module and paste following code in your module file:

&lt;?php

/**
 * Implementation of hook_boot().
 *
 * Ask for user credentials and try to authenticate.
 */
function foo_boot() {
  require_once DRUPAL_ROOT . '/includes/password.inc';

  if (isset($_SERVER['PHP_AUTH_USER']) &amp;&amp; isset($_SERVER['PHP_AUTH_PW'])) {
    $query = "SELECT pass FROM {users} WHERE name = :name";
    $result = db_query($query, array(':name' =&gt; $_SERVER['PHP_AUTH_USER']));
    $account = new stdClass();
    foreach ($result as $row) {
      $account-&gt;pass = $row-&gt;pass;
    }
    if (isset($account-&gt;pass)) {
      if (user_check_password($_SERVER['PHP_AUTH_PW'], $account)) {
        return;
      }
    }
  }

  header('WWW-Authenticate: Basic realm="Development"');
  header('HTTP/1.0 401 Unauthorized');
  exit;
}


This uses HTTP Authentication and checks the Drupal Database for a valid username and password.

If you have any problems with PHP CLI, Drush or cron, you can add following code in the hook:

  // Allow cron through
  if (basename($_SERVER['PHP_SELF']) == 'cron.php') {
    return;
  }  

  // Allow PHP CLI/Drush through
  if (isset($_SERVER['argc'])) {
    if (php_sapi_name() == 'cli' || (is_numeric($_SERVER['argc']) &amp;&amp; $_SERVER['argc'] &gt; 0)) {
      return;
    }
  }