The science of webometrics (also cybermetrics) tries to measure the World Wide Web to get knowledge about the number and types of hyperlinks, structure of the World Wide Web and usage patterns. According to Björneborn and Ingwersen (2004), the definition of webometrics is "the study of the quantitative aspects of the construction and use of information resources, structures and technologies on the Web drawing on bibliometric and informetric approaches." The term “webometrics” was first coined by Almind and Ingwersen (1997). A second definition of webometrics has also been introduced, "the study of web-based content with primarily quantitative methods for social science research goals using techniques that are not specific to one field of study" (Thelwall, 2009), which emphasises a small subset of relatively applied methods for use in the wider social sciences. The purpose of this alternative definition was to help publicise appropriate methods outside of the information science discipline rather than to replace the original definition within information science.
One relatively straightforward measure is the "Web Impact Factor" (WIF) introduced by Ingwersen (1998). The WIF measure may be defined as the number of web pages in a web site receiving links from other web sites, divided by the number of web pages published in the site that are accessible to the crawler. However the use of WIF has been disregarded due to the mathematical artifacts derived from power law distributions of these variables. Other similar indicators using size of the institution instead of number of webpages have been proved more useful.
Since 2004 the Webometrics ranking of world universities has been offering information about more than 18,000 universities ranked according to indicators measuring web presence and impact (link visibility). There are also Rankings Web devoted to Research Centers, Hospitals, Repositories and Business Schools. Since 2004, the Ranking Web is published twice a year (January and July). Web presence measures the activity and visibility of the institutions and it is a good indicator of impact and prestige of universities. Rank summarizes the global performance of the University, provides information for candidate students and scholars, and reflects the commitment to the dissemination of scientific knowledge. If the web performance of an institution is below the expected position according to their academic excellence, university authorities should reconsider their web policy, promoting substantial increases of the volume and quality of their electronic publications. The original aim of the Ranking was to promote Web publication. Supporting Open Access initiatives, electronic access to scientific publications and to other academic material are the primary targets. However web indicators are very useful for ranking purposes too as they are not based on number of visits or page design but on the global performance and visibility of the universities. As other rankings focused only on a few relevant aspects, specially research results, web indicators based ranking reflects better the whole picture, as many other activities of professors and researchers are showed by their web presence. There are some purposes and goals of using Rankings:
1. Assessment of higher education (processes, and outputs) in the Web.