Data preprocessing plays a main role in data mining projects. Preprocessing is the ground work of data mining. Before performing the mining process the raw data has to be preprocessed in order to improve the quality of data to be mined. This mining involves the automatic filtering of patterns from various web pages of a web site. This helps the web developers to determine the value of specific web pages, this paper discusses the importance of data preprocessing methods and various steps involved in getting the required web page effectively.