If you run a website that receives a substantial amount of traffic then you've already experienced one of the worst things that can happen to a website, and that is it goes down and you don't know about it.
You notice how most web hosts say 99% uptime? The reason why you don't see 100% as often is because they simply can't guarantee that. If your running dynamic CMS platforms like WordPres, Joomla and Drupal then you most certainly know those tools kick the shit out of a unprepared server. Even with the help of Cache technology and CDN support sites still go down, and the worst part about it is that you don't know when it does.
Just 2 weeks ago one of my servers was down for an entire day, it was a Sunday so I wasn't even online. It wasn't until Monday morning that I found out about it from one of the regular visitors to my site. So for a whole day 3 of my sites were down and thus lost me a ton of money.
And it's not like web hosting companies don't offer website monitoring, they do but it's not very good and if it's a server issue then the notification tool that's running on the server is down as well.
I wrote about this on Facebook and as soon as I posted it a ad showed up about a website monitoring service called Site24x7 (good job with the ad targeting Facebook).
Of course I immediately checked it out, and the service is straight forward, they monitor your website 24×7 in frequencies of minutes, hours or day the choice is yours. They go even further than that by offering monitoring services for Web Applications, DNS, Mail Server, WPA, Port, POP, SMTP, Ping and SSL Certificate. One of the best things about the service is that as soon as your site goes down, within a minute of the downtime you receive a text message to your mobile device letting you know.
Some screen shots of the back-end of the service below:
If you've experienced downtime on your website more than 3 times then a service like Site24x7 is definitely worth a shot.
Check them out, Site24x7.