When your WordPress blog has trouble connecting with the database, it returns a nice “Error Establishing a database connection”.

wordpress-database-error

Instead of losing visitors, db-error.php might be the useful solution.
You should create and place it in the wp-content folder. After that paste this short code in it.

<?php
// db-error.php

$host=$_SERVER['HTTP_HOST'];
$uri=urlencode($_SERVER['REQUEST_URI']);
header("Location: http://google.com/search?q=cache:$host$uri");
exit();

?>

the visitor is automatically redirected to the Google cache of the requested page. This avoids losing a visitor.