You might want to check the following publication: Ackland, R. (2013), Web Social Science: Concepts, Data and Tools for Social Scientists in the Digital Age, London: Sage. Chapter 2 of the book explores different aspects relating to web content analysis.
For an example that might be of interest, you can read about how we 'mined' online school inspection reports from a UK website to see what was said about textbook use in England; see:
Chapter Mathematics textbook use in England: mining Ofsted reports f...