One of the basic methods of web usage mining are association rules that indicate relationships among common use of web pages. Positive and confined negative association rules are the components of the new quality measures: Positive and Negative Quality function, respectively. These functions are used to evaluate the quality of hyperlinks existing on web pages. A number of statistics and the expert validation revealed the usefulness of association rules for the assessment of hyperlink usability. Categories and Subject Descriptors H.5.4 [Information interfaces and presentation]: Hypertext/Hypermedia – navigation General Terms Design, Management, Measurement, Verification Keywords hyperlink assessment, negative association rules, web mining