The use of Wikipedia as an information source is becoming increasingly popular. Several studies have shown that its information quality is high. Normally, when considering information trust, the source of information is an important factor. However, because of the open-source nature of Wikipedia articles, their sources remain mostly unknown. This means that other features need to be used to assess the trustworthiness of the articles. We describe article features - such as images and references - which lay Wikipedia readers use to estimate trustworthiness. The quality and the topics of the articles are manipulated in an experiment to reproduce the varying quality on Wikipedia and the familiarity of the readers with the topics. We show that the three most important features are textual features, references and images.