One of the historical uses for web measurement tools that retain value is the ability to identify and diagnose error messages that your visitors may be seeing.
Nobody is perfect, they say, and web programmers are often less perfect than most. Constrained by tight deadlines, scope creep, and poorly defined standards for web page development, web programmers do the best they can. Unfortunately, the best is sometimes not good enough, and errors arise. One of the most valuable uses of your web measurement application is the identification of errors so any problems can be quickly corrected.
There are many types of mistakes that can happen, but not all of them can be traced with typical web measurement tools alone. Here are a handful of the most common that can be tracked.
There are services that specialize in web site monitoring designed to ping your web site regularly to ensure that it is accessible and that your web servers are handling page requests in acceptable amount of time. You can set up alerts for when something is wrong. Typical web measurement tools on the other hand do not provide adequate support for measuring these aspects, but it is possible to integrate response and availability into your web measurement application to provide a more holistic view of the situation [#Hack Measure Site Performance].
If a visitor requests a URL that is unavailable, the web server will return the classic ...