The increasing need to check Web site accessibility has stimulated interest in tools to aid the various activities involved. While some tools for this purpose already exist, we believe that there is a demand for making their support more flexible. In particular, there is often a need for validation of multiple sets of guidelines, repairing Web pages and providing better reports for the evaluators. In this paper, we discuss such issues and how we have addressed them in the design of MAGENTA, our new tool for supporting inspection-based evaluation of accessibility and usability guidelines.