If you use shared hosting, this reverse DNS look-up site can provide some insight into your server environment. Shared hosting is typically cheaper and can work perfectly fine with the right balance. If one website on your shared server is experiencing the Digg Effect, however, your site might go down as well. It might be time to look for new hosting if it happens too frequently.
You can find out exactly how many other sites are hosted on your server and if there is any questionable content. I can’t explain it any better than they did. From their website:
For those on shared hosting, myIPneighbors IP search is a great way to find out who your neighbors are or just to see how many other websites your hosting company hosts your server.
Is your website packed into a crowded host with hundreds of other sites? Or is there questionable content being hosted side by side with your site? If so, it may be time to look for a better host.
Visit myIPneighbors and run a scan against your domain to see who else lives on the block.