Abstract: This research combines both computer and statistical knowledge in performing a post implementation review of users perception to the usability of IUO (Igbinedion University Okada) online portal system based on the four usability factors (compatibility and helpfulness, subjective satisfaction, efficiency and accuracy and learnability) earlier identified by Omorogiuwa and Chiemeke. The 50 items online questionnaire designed by human factor resource group was adopted to gather information about the usability of IUO online portal system. The respondents were mainly students of IUO, who are the major users of the online portal system for course registration, checking of results, admission clearance etc. The data was gathered between January to June 2007. A further detailed analysis of the various users perception of these factors revealed that there are differences in perceptions among and between the users of IUO online portal system and even where there are differences, are such differences statistically significant? Analysis of Variance (ANOVA) and post hoc test tools in SPSS 14 were used in carrying out further analysis. Among the 4 factors used for the post implementation review, ANOVA test shows that students perception is only significantly different to the subjective satisfaction factor. The post hoc test revealed a significant difference in the perception of students to the subjective satisfaction of IUO online portal system only between students in health science and social science/business management science.