The internet has become a key environment for children's learning and leisure at an increasing early age. Yet, little is known about what children understand about the internet. We conducted semi-structured interviews with 111 children aged five to nine to assess their notions about the internet, the authorship of online content and the trustworthiness they attribute to it. Considering the socio-cognitive advances throughout these ages, we expected a significant improvement in children's concept of the internet. However, the results showed modest age differences, and only in some basic notions (e.g., internet functions). Misconceptions about the internet and naïve ideas about the reliability of its content were present at all ages. Only a very few older children envisaged the risk of finding malicious information online and the need to consult other sources in case of doubt. We discuss the necessity to address children's misconceptions at least from the beginning of primary school, when most of them are cognitively ready to understand many of the issues addressed in this study, provided they receive guided instruction.