In this paper we focus on categorization task for web sites. We compare some quantitative characteristics of existing web directories, analyze vocabulary used in descriptions of web sites in Yahoo web directory and propose an approach to automatically categorize web sites. Our approach is based on the novel concept of salient words. Experimental evaluation compares two realizations of proposed concept. The former uses words typical for just category, while the latter uses words typical for one or few categories. Results show that there is a limitation of using single vocabulary based method to properly categorize such heterogeneous space as is the World Wide Web.