Automatic classification of Web pages is an effective way to organise the vast amount of information and to assist in retrieving relevant information from the Internet. Although many automatic classification systems have been proposed, most of them ignore the conflict between the fixed number of categories and the growing number of Web pages being added into the systems. They also require searching through all existing categories to make any classification. This article proposes a dynamic and hierarchical classification system that is capable of adding new categories as required, organising the Web pages into a tree structure, and classifying Web pages by searching through only one path of the tree. The proposed single‐path search technique reduces the search complexity from θ(n) to θ(log(n)). Test results show that the system improves the accuracy of classification by 6 percent in comparison to related systems. The dynamic‐category expansion technique also achieves satisfying results for adding new categories into the system as required.