Apache and Lighttpd configure mod_rewrite for temporary site outage

Here's a nice howto
on using mod_rewrite under Apache and Lighttpd for temporary site
outages. This tip will help you to disable a site for maintenance using
mod_rewrite without redirecting url. Both Lighttpd and Apache webserver
allows you to send this message to client using server side rewriting
using mod_rewrite and php. This is useful if you are running popular
database driven community or e-commerce website. Error 503 informs
search engine that site is temporary out of service. A good idea if
your websites is heavily depends upon search engine for selling
products and services.