Employing scientific investigation is essential to understanding hypermedia processes and products, making hypermedia authoring a science rather than an art. This paper describes a case study aimed at validating empirically metrics proposed to measure the development effort involved in authoring a hypermedia application. The case study is one of the empirical evaluations that we have conducted and it has been planned according to a scientific method of research. Our objective is to improve hypermedia authoring by measuring some quality characteristics of hypermedia applications and the processes involved in developing hypermedia applications.