As part of their corporate record, many academic institutions are setting up institutional repositories to hold copies of work written by members of their staff. Institutions often regard this as good publicity for the research and teaching undertaken at the institution and therefore wish to make the repository open.
Likewise an author may wish to invite comment on his/her work from others working in the same field by placing a copy on an open web site. There is a risk for the author that a publisher will regard posting to a web site as prior publication if the pre-print is posted before acceptance for publication but posting to a web site after acceptance and before publication is a right to be negotiated. May publishers accept that a pre-print or a post print of the article is posted in an institutional repository.
Clearly the posting of a journal article to an open web site carries greater risks for a publisher, although it may not necessarily be against the publisher's interests. If permitted this right not covers the posting of the publisher's own formatted version but publishers sometimes provide a PDF for this purpose. The publisher's copyright notice should be attached to the author's text along with a full reference and hyperlink to the published version. The author may be expected to provide a hyperlink to the publisher's web site.
In scholarly communication several definitions of pre prints, post prints and definitive versions are used. The definitions used in this part of the toolbox link up with the definitions used by learned society publishers but other definitions can be found.