This program spiders all your domains, emails if any are found to be down. Site Spider is a "spider" that queries web connectivity to any number of domains to see that are responding. A useful tool if you are responsible for a large number of domains and want to make sure that not only is the server itself up but the website is accepting http request and serving up pages to your site. It can run off cron so you can set it to spider as regularly as you require.