The goal of this project, is to demonstrate the concept of a web browser based measurement component using Mozilla. Mozilla is interesting as a container for WAM measurement systems due to Mozillas Accessibility architecture which is used by 3rd party software like screen readers, magnifiers, and voice dictation software, which need information about document content, UI controls and events like changes of focus. Mozilla supports two accessibility APIs: MSAA on Windows[MSAA] and ATK on Linux and Unix[ATK]. Mozilla has also implemented an accessibility model into the browser consisting of transformations from a non-accessiblie DOM tree to an accessible DOM tree. The hypothesis is that a browser based measurement component should simplify some accessibility measurements considerably, like identifying screen flickering, redirection, JavaScript links or spawned windows, by subscribing to events via the accessibility interface or the DOM tree. The measurement component must conform to the web services based plug-in interface for the EIAO Web Accessibility Observatory, so that the measurements can be used for large scale accessibility assessments by the Observatory