Website Down

What Should i do when my website is down? i know to add page under construction, i m asking apart from that what steps i should take?

You should put a 503.

<?php
    header('HTTP/1.1 503 Service Temporarily Unavailable');
    header('Status: 503 Service Temporarily Unavailable');
    header('Retry-After: 43200'); //12 hours
?>
 <html>
 <head><title>Unavailable</title></head>
 <body><h1>503 - Temporarily Unavailable</h1><h3>Come Back Soon!</h3></body>
 </html>

You can put pretty much whatever you want on the page as long as the header reads 503 so that Search Engines know you’re working on it.