Having paid for web hosting, you will naturally want to make sure that you are getting what you paid for. If your hosting service is not giving you the amount of working time that you expect from it, you are entitled to know why, and to find this out as soon as it happens. You cannot constantly be sat monitoring your site – and if you have more than one, this is impossible anyway, so it may be a good idea to pay for a dedicated website monitoring service that will constantly check the status of your site.
The way this works is that dedicated software is used to access your site once every three minutes (the time may vary, but the principle is the same with all services of this nature). As long as the service gets the response it is expecting – an active website – it will take no further action, and simply check again as soon as the time period has elapsed. When it gets a message saying that the site is down, it checks again seconds later using a different IP address. If it gets the same response, it will contact you.
Generally, this will be done by means of a mobile device such as a cell phone or a pager, and will be a short message telling you that your website is down. If this is during an already advertised period of downtime, there is nothing more you need to do. If not, then you can contact your hosting service alerting them to the fact, and get the problem fixed as quickly as possible.