The approach of the Web accessibility is necessary for all the people to be able to use websites. As the visual elements are very important factors in the website, in our previous study, the visibility of young adults, the elderly and dichromatic vision was evaluated using the simulation filters. And we made a model of linear discriminant function for predicting the website visibility. In this report, in order to improve the visibility predictive formula, we made a model of quadratic discriminant function. And the accuracy of the calculated predictive formula was evaluated based on the visual feature. As the results, both discrimination functions had a high correlation with the visual feature. However, the correlation of the linear discriminant function was stronger than the quadratic discriminant function. Therefore, it was shown that the linear discriminant function strongly reflected the visual feature.