: Software practitioners recognise the importance of realistic estimates of effort for the successful management of software projects, the Web being no exception. Estimates are necessary throughout the whole development life cycle. They are fundamental when bidding for a contract or when determining a project's feasibility in terms of cost-benefit analysis. In addition, they allow project managers and development organisations to manage resources effectively. Size, which can be described in terms of length, functionality and complexity, is often a major determinant of effort. Most effort prediction models to date concentrate on functional measures of size, although length and complexity are also essential aspects of size. A case study evalualion is described, in which size metrics characterising length, complexity and functionality are obtained and used to generate effort prediction models for Web authoring and design. The comparison of these size metrics as effort predictors is d...