As Web sites begin to realize the advantages of engaging users in more extended interactions involving information and communication, the log files recording Web usage become more complex. While Web usage mining provides for the syntactic specification of structured patterns like association rules or (generalized) sequences, it is less clear how to analyze and visualize usage data involving longer patterns with little expected structure, without losing an overview of the whole of all paths. In this paper, concept hierarchies are used as a basic method of aggregating Web pages. Interval-based coarsening is then proposed as a method for representing sequences at different levels of abstraction. The tool STRATDYN that implements these methods uses χ² testing and coarsened stratograms. Stratograms with uniform or differential coarsening provide various detail-and-context views of actual and intended Web usage. Relations to the measures support and confidence, and ways of analyzing generalized sequences are shown. A case study of agent-supported shopping in an E-commerce site illustrates the formalism.