This article describes 1) the special features and accessibility of an innovative web-based practice instrument (WebMA) designed with randomized short-answer, matching and multiple choice items incorporated with automatically adapted feedback for middle school students; and 2) an exploratory study that compares the effects and contributions of web-based practice on students' learning processes with that of traditional paper-and-pencil practice. With multiple practices and immediate adapted feedback, the web-based group performed significantly better than the paper-and-pencil group on both fraction and decimal operations at the end of the study. On an average, female students gained a higher score on the post-test. However, females were distracted by the web features more than males. Students enthusiastically expressed their desires of having more of this dynamic and interactive practice by the end of the study.