This paper reports on a study that examined citation practice in a set of scholarly papers. After evaluating 2162 bibliographic references it was found that 48.1% (1041) of all citations used in the papers referred to a Web-located resource. A significant number of references to URLs were found to be missing (45.8%) and an evaluation of these Web-located citations allowed the average half-life (4.8 years) for these missing resources to be determined. The study also examined the composition of the top-level domains associated with resource loss as well as the proportional use of Web-located resources in individual articles. The proportional use of Web-located resources in individual articles and their corresponding evaluation for disappearance has not been previously documented. The paper utilised the proportional Web citation aspect of articles in proposing a Web-resource contribution index and a Web-citation use-loss grid that may aid future authors, editors and, in particular, researchers in investigating this growing aspect of citation behaviour.