comparative evaluation of websites of united states national library of medicine and iranian national library of medicine

introduction: nowadays and with the increasing role of the worldwide web as one of the most important sources of information on the one hand, and the enhancement of its usability on the other, it is necessary for the web designers and developers to be familiar with the criteria that make a web portal usable. therefore, the present study aimed to provide knowledge about the criteria of usability in united states national library of medicine (nlm) in comparison to iranian national library of medicine (inlm). methods: taking a critical approach, this article examined web portal of nlm in comparison to inlm, in order to conduct a reliable assessment. the tools for data collection was an explanatory checklist, developed by the researchers based on the review of the literatures consisted of 159 components. desired portals were measured by it. in order to analyze research findings, descriptive statistics (frequency and percentage) used. results: in general, the results showed that the evaluation of usability in nlm portal, compared to the overall assessment in accordance with all the sub-criteria, in index portal, (with 676 points), was 96%, and it was 48% in inlm. conclusion: considering the increase of expansion for web portals and their roles, web portal usability evaluation ensures web designers about the usability of their websites for satisfying their general users. according to the value place of national library as the golden gateway to access quick easy and unlimited medical information, considering its web usability can be useful. obviously, each information service exists for the sole purpose of satisfying its users, and all its activities, services and products are geared towards this purpose. how well this purpose is served is a measure of the usefulness of that information service.