In this paper we describe a technique for automatic construction of ontology, a semantic representation of a conceptualization, for any domain, organization or enterprise whose Web site is existent with quiet a big mine of information. An user interactive system is developed with the help of which any organization, which has a Web site to maintain data, but has no corresponding semantic mark up, can automatically construct the ontology and further use that to model domain knowledge and make use of various Semantic Web applications like Semantic Web search engine etc. The automated construction of ontology will facilitate further the growth, popularity and usage of the Semantic Web and Semantic Web technologies as well as serve as a basis for Artificial Intelligence reasoning.