This paper investigates how the presence of a minority language closely related to the majority language is received and treated on the World Wide Web. Specifically, it deals with the acceptability and treatment of texts written in Slovak in the .cz domain, which belongs to the Czech Republic, more than a decade after the split of Czechoslovakia. Employing Language Management Theory and focusing on membership categorisation, the investigation first examines user comments which refer to the use of Slovak on .cz websites as inadequate or problematic. The analysis then proceeds in two directions: first, it deals with users' expectations regarding the use of Slovak on specific websites. Second, it focuses on how users and the website editors subsequently managed the problematic deviations from these expectations. As a result, the study centres around three phenomena which were shown to be relevant for the online participants: Internet nationalism, the intelligibility of Slovak to Czechs and the searchability of webpages in a closely related language.