Using the analysis of the so-called For example, you can find out in the server response headers to HTTP queries what programming language and server infrastructure was used to build the application. It is also useful to analyze error messages and source code. The figure below shows an example server response from which you can deduce that the application you are investigating was written using .NET version 4.0.30319 and hosted on internet information services version 10.0. 
Figure. Sample server response with sensitive data. Source: [Own study]
