Information growth in the web medium has required the necessity of archiving these information to transmit them to future generations. Web archiving is a versatile application which covers technical, legal and organizational dimensions. Any stage within the life cycle of digital information is critically important for the information in web environment. All over the world, many countries have started web archiving efforts through the leadership of their national libraries and attempted to carry these initiatives on a legal bases. In the light of these developments, this paper examines the necessity and major techniques in web archiving and it also discuss national and international web archiving projects.