We study the effort needed for designing Web applications from an empirical point of view. The design phase forms an important part of the overall effort needed to develop a Web application, since the use of tools can help automate the implementation phase. We carried out an empirical study with students of an advanced university class that used W2000 as a Web application design technique. Our first goal was to compare the relative importance of each design activity. Second, we tried to assess the accuracy of a priori design effort predictions and the influence of factors on the effort needed for each design activity. Third, we also studied the quality of the designs obtained.