The authors compared Web usability definitions, collected from library professionals at academic institutions of the Association of Research Libraries (ARL) through online surveys in 2007 and 2012, to determine whether library practitioners' perspectives had altered as information technologies evolved during this time. The authors applied three techniques of statistical data analysis--t-tests, cluster analyses, and the Mantel test--for comparisons. The results indicated significant increased emphases on the "Interface/Design" and "Effectiveness" attributes in the 2012 data set. This increase may be due to the rise in the use of mobile devices for information access, driving practitioners to place a stronger emphasis on these attributes.