In this paper, we explore teens' mental models of public library websites for teens (teen library websites/TLWs), specifically favorite websites as they relate to prior knowledge and experience. Thirty teen participants from three public libraries within three demographically diverse locations in New Jersey took part in the study. Each participant completed a questionnaire, a drawing task, and a semi-structured individual interview. During the semi-structured interview, participants described their drawings in detail, discussed and demonstrated their favorite websites and evaluated current TLWs. The results showed that teen public library users hold multiple mental models of TLWs. In addition, favorite websites data provided some understanding of the role of prior knowledge and experience in teens' use and expectations of TLWs. Based on analysis of the data, we offer design recommendations for making TLWs better match teens' design and use expectations and preferences.