Uptime periodically requests a page from your Web server. If the site is unreachable, it sends you an email, followed by another when it becomes reachable again.
Measure of the time period which the web server has been online. For example, a server can have an uptime of 100 days - meaning it has not failed during the last 100 days and has ran non-stop during that period. Can also be expressed in percentages. Example: uptime of 99.9%. See SLA Back to up
Time during which something is functioning or operational.