Achecker® is an open source Web accessibility evaluation tool. It can be used to review the accessibility of Web pages based on a variety international accessibility guidelines. The public Achecker® links to the SSB Bart AMP Express evaluation site. You can also download Achecker® to setup your own version. Evaluating accessibility with Achecker® is an interactive ongoing process. AChecker knows when it is unable to identify a potential problem and will ask the evaluator to conduct manual check(s). Because Web content often changes, Achecker®r can be used to monitor the accessibility of Web content as it evolves. It also allows users to create specialized accessibility guidelines and new checks for a system as technology develops. It is an open source system, so those who want to develop expertise in accessibility evaluation have full access to the inner workings of the system, all the accessibility checks and the solutions for fixing problems found by the system, and a full range of test files that verify exactly what each accessibility check is checking.