For supporting the education of debugging skills, we propose a system for generating error correction questions of programs and checking the correctness. The system generates HTML files for answering questions and CGI programs for checking answers. Learners read and answer questions on Web browsers. For management of error injection, we have analyzed types of errors and defined the processes of error injection as code transformation patterns. The system synthesizes code fragments including errors by transforming correct code fragments according to the selected patterns. Full coverage of all possible answers is difficult. Instead, we have adopted a strategy to restrict editable points and possible answers from the educational view. To confirm the effectiveness of the system, we have generated questions using several examples and applied them to a programming exercise as an evaluation experiment. [For the complete proceedings, see ED557189.]