assessment of web citation accessibility and decay of health information and medical librarianship articles indexed in isi

introduction: web citations (urls) are at risk of decay and can be easily fade because of the variable and unstable nature of the internet. so, the purpose of this research was to assess web citation accessibility and decay of articles published in journal of the medical library association (jmla). methods: in this applied– descriptive study, jmla articles (231) in a seven year period (from 2002 to 2008) downloaded from magazines archives and the articles that have web citation (175), determined. then, all of urls were tested to specify their accessibility and decay. when we failed to directly access the urls, we used internet explorer, internet archive and google search engine to access missing urls. obtained data analyzed using excel software to determine the half-life of web citations and the reasons for the url failure. then gathered the result of these tests and analyzed them using microsoft excel to distinguish cause of these failure and to count web citations half-life. results: 76 percent of articles had web citation and the average of web citation per article was 5 url. from 1049 cited url, 31 percent was inaccessible, but by searching these urls, the decay decreased to 13 percent. the majority of errors were the 404 (not found) and the average of web citations half-life was approximately 7 years. conclusion: the decay of urls is a big problem that can not be ignored because urls are increasingly used and lost in scientific articles, the decay of urls will continue until better preservation policies (such as internet archive) are adopted.