Many libraries—especially large, urban libraries—have large collections of photographs, digital images, rare and fragile books, artifacts and manuscripts available for public viewing and use. Digitization and digital preservation of these works is an ongoing effort, usually funded by grants or philanthropy. In 2005, the New York Public Library offered the "NYPL Digital Gallery" which made a collection of 275,000 images viewable over the web; while most of the contents are in the public domain, some images are still subject to copyright rules. Limited funding, copyright restrictions, a lack of expertise and poor provenance are barriers to the large-scale digitization of libraries' special collections.