This article analyzes folk-linguistic photo blogging as an example of twenty-first-century grassroots prescriptivism. Photo blogs engaged in grassroots prescriptivism usually focus on one specific linguistic phenomenon and collect visual evidence of its usage. Through the overt or covert language policing involved in such displays, folk-linguistic photo blogs contribute to the digital enregisterment of the linguistic practices they focus on as nonstandard or uneducated. This process is closely examined in a case study on emphatic quotation marks, a nonstandard form of punctuation that has been termed ‘greengrocer's quotes’, and its concomitant folk-linguistic photo blog. It is argued here that much of the persuasive power of such blogs can be attributed to their reliance on photographic material depicting signage in public space, and thus on the kind of visual semiotics that also informs many recent approaches in sociolinguistics. The simultaneity of these two phenomena is critically discussed. (Visual semiotics, enregisterment, computer-mediated communication, grassroots prescriptivism, emphatic quotation)*