Web servers are not perfect and they crash. I use InMotion Hosting for my web servers and they guarantee a 99.9% uptime... it's not 100%. Yesterday InMotion was having some data center issues and I knew about it within a minute of the servers going down because of a great tool from Uptime Robot. Their free plan will ping your website every 5 minutes and you can add up to 50 websites. If you need more monitors or want them to ping your website more often, they offer very competitive pricing.
If you have a website you should use Uptime Robot. Knowing there's a problem is step one to fixing it. If you need website, graphic design or marketing services, please contact me today.