The web host uptime guarantee

In my opinion, the single most important thing in choosing a web host is the uptime guarantee. The uptime guarantee is usually stated as a percentage and refers to the amount of time your web site will be available for all to see on the web. So a 99.9% uptime guarantee means that your site would be on the net 99.9% of the time. If we convert the percentages into actual time, a 99.9% uptime means that the web site would be down or offline for 8.76 hours (0.365 days) in a year. For most of us, this is just fine.

If a web host company offers anything less than 99% uptime - move on.