The aim of this thesis was to determine if there were usability score differences between languages on Swiss museum’s multilingual websites. Usability is one of the keys to keep a visitor on a website. In our case study, we conducted a heuristic evaluation of a corpus of 28 pages from 14 websites in three languages (French, German, English). Our findings indicate that usability levels differ across target languages and vary depending on the language combination and the criterion analyzed. Our study also confirmed that the usability of a website tends to be affected negatively by localization.