As Web applications are becoming more and more complex, there is an increasing concern about how to retrieve and navigate effectively to new information. This has driven many researchers to investigate into how people navigate within Web applications, and how the Web applications should be modeled and designed. In the work, a novel approach is proposed to modeling Web navigation for its formal representation using FSM (Finite State Machine) and Z language. It models user behavior in page navigation by FSM and specifies Web pages, hyperlinks, page-scoped variables and frames using Z. Such provides the users with two different views, one of which concerns behavioral navigability and another concerns page linkage, of a Web application. The proposed approach affords an underlying guideline for modeling Web navigation combining FSM with Z.