Many providers offer some kind of uptime guarantee. Be sure to read the small print in order to fully understand what that means. I’ve dealt with providers which the guarantee was only for the website and not for email. I went a full day without functioning email and the host refused to give me any discount on that month’s service charges.
Many providers give a 99.9% uptime guarantee. This means that the provider guarantees that their servers will not go down for more than 8 hours per year or less than 45 minutes each month. Of course, if you’re in the middle of a big marketing campaign, 45 minutes can be crucial.
If a provider fails to meet their guaranteed up time, you can usually get your hosting charges waived for the month. If it happens regularly, you can literally go months without having to pay fees. Sounds nice, but it’s really not adequate compensation for the amount of traffic, and perhaps business, you lose while your website or email is not functioning as it should. If you are currently with a host that goes down more than a couple times a year, you may want to reconsider who you host your website with.