Hosting a website involves understanding various issues about a web hosting service including monitor server uptime offered.
Most web hosting companies offer 99% and more uptime but this is neither constant nor is it the same for all websites hosted by the company. It is absolutely essential to monitor server uptime of all web hosting services before finally choosing one.
One very simple method to monitor server uptime is to watch the performance of other websites on that host.
However, this will not give you a clear idea as the website you are monitoring may be on a different server than yours. Another way is to use software that is available in abundance on the Internet to monitor server uptime. Here again the same problem of not knowing whether you are monitoring the same server or not arises.
The best option that many in this industry feel to monitor server uptime is to actually host a website for a short while with the web hosting company and then monitor server uptime of your website very closely, after which you can decide whether the company is providing what it promised or not. Most web hosting companies allow you a test trial of hosting and hence make it possible for you to monitor server uptime free of cost. Additionally, it would help if you can enroll the services of a third party to monitor server uptime of your website so as to get accurate data.
If the website does not offer a free trial or test plan, then you should opt for the minimum plan available, say on a monthly basis and then monitor server uptime of your website during that month. This gives you the freedom of changing hosting companies in case you are not satisfied with the service. However, you should never opt for hosting for longer periods say six months or a year before you actually understand the quality of the monitor server uptime offered by the company.