The number of works made freely accessible on the Web by institutions joined to Open Archive Initiatives such as libraries, research institutions, scientific and cultural archives, is constantly growing. Until now some international agreements among key players of Open Access approach have been established but the low level of standardization and the lack of a digital resource and repository certification authority prevents any quality control on the works and subsequently their trustable dissemination within the cultural and scientific community. In this scenario, the benefit of having freely accessible resources is lost. The study proposed in this paper aims at providing a statistical analysis of the state of art of OA implementations in order to outline weak practices, propose assessment metrics for self analysis and stimulate a general improvement of the quality of OA implementations.