Due to the advances made in Information and Communication Technologies (ICT), e-Government users can easily use the available services from places and at time that are convenient to them through WWW browsers. To easily and securely provide the required services through Information Technology (IT) has been an important issue in e-Government. In this article, the authors propose an explicit classification of e-Government applications and some challenges and obstacles in e-Government considered from four perspectives. Finally, a comprehensive view of some critical success factors in e-Government is proposed.