In this day and age, web applications are virtually ubiquitous. Some kinds of websites or a collection of web pages is typically the final product or the service of a complex structure that comprises different databases, application servers, web servers, proxies, network balancers and appliances, and more. When it comes to monitoring duties, it makes sense to go just a step further and monitor a resulting site or web page in addition to all the backend assets that enable the said page. The advantages as far as warnings and notifications go, are fairly limited, as failure to reach a web page is certainly a critical event. But it hardly gives any insight into what may be the actual problem if you haven't set up the correct metrics and triggers on the backend side. On the other hand, it may be crucial to have a collection of data about a website's performance. In order to anticipate possible problems, substantiate SLA reporting, and plan for hardware or software upgrades...