This Technical Report defines statistics, terms and quality criteria for Web archiving. It considers the needs and practices across a wide range of organisations such as libraries, archives, museums, research centres and heritage foundations. The examples mentioned are taken from the library sector, because libraries, especially national libraries, have taken up the new task of Web archiving in the context of legal deposit. This should in no way be taken to undermine the important contributions of institutions which are not libraries. Neither does it reduce the principal applicability of this Technical Report for heritage institutions and archiving professionals.