Conservation:

"It is important to note that a microenvironment is created when a photograph is placed in a frame for exhibition. Use unbuffered ragboard mats, and frame photographs with archivally sound materials. Use ultraviolet filtering plexiglass to help protect the photographs during light exposure." --The American Institute For Conservation Of Historic & Artistic Works: 

Some resources related to conservation:

American Association of Museums
American Association for State and Local History
American Institute for Conservation
American National Standards Institute
Conservation Center for Art and Historic Artifacts
Conservation Online
International Zeolite Association
Gerald Ford Conservation Center
Getty Conservation Institute
Library of Congress
The Smithsonian Institution's Center for Materials Research and Education