Evidence suggests that guidelines employed in conformance testing do not catch all the accessibility barriers encountered by users on the Web. Since accessibility is strongly tied to the users’ experience there is a subjective perception of accessibility barriers and their severity. What is more, not only intangible qualities characterise the way in which these barriers are perceived, but also navigation styles, age, onset, expertise and abilities play a key role. In order to overcome the limitations of conformance testing and catch the problems that emerge during the interaction we propose a user-interaction-driven method to automatically report accessibility problems. To do so, we initially isolate the problematic situations faced by users and the tactics employed in such situations. These tactics are considered behavioural markers of cognitive processes that indicate problematic situations; the presence of tactics denotes the presence of problems. Then, we design and deploy algorithms to automatically detect the exhibition of these tactics and consequently detect problematic situations. WebTactics, a tool that unobtrusively detects and reports the problematic situations undergone by visually disabled users illustrates the method we propose.