Complex and multi-functional museum web application Eternitas was presented in the paper. Highly user-oriented to museum professionals, primarily to curators, documentarians, and managers, this software presents an integral part of broader information system MISS, developed at the National Museum in Belgrade, Serbia. In last two decades that museum information system has successfully gathered data on nearly 250,000 objects from entire Serbian museums' fund. In the beginning of attentive state ministry supported project in 1996, strategic development study of the Museum Information System of Serbia (MISS) had identified 11 subsystems, e.g. implementation modules. Subsequently, the very first module, Central Register of Movable Cultural Goods of Serbia (CR), had been introduced into almost 50 Serbian museums' practice. In the second stage, starting from 2007, a contemporary relational database has been created, in the scope of basic processes of two MISS subsystems - Museum Fund Acquisitions, and Scientific and Expert Processing. Furthermore, new developped applicaton Eternitas enables not only complex professional data managing, but their public web presenations, as well. Through a museum professional practice case study its functionality and distinctiveness are breifly illustrated.