UNLABELLED: In today's competitive digital economy, effective web design is crucial for shaping user perceptions of organizations. While prior research has primarily focused on a single or few low-level design variables-such as color choices or banner layouts-this study explores webpage prototypicality-the extent to which a webpage aligns with typical design conventions in its genre-as an overarching design variable that encompasses various sub-variables (e.g., navigation structure, color schemes, and layout organization). Drawing on the elaboration likelihood model, we explore how webpage prototypicality interacts with message strength and users' cognitive elaboration to affect users' attitudes toward an organization. Through an online experiment on commercial banking websites, we found that higher prototypicality significantly improves users' attitudes, specifically their general attitude towards the banks and the banks' attractiveness as employers, highlighting its role as an effective design variable. Furthermore, our study shows that prototypicality plays a mediating role in the effects of message strength on users' attitudes. This research contributes to research on web design in the fields of information systems and human-computer interaction and provides guidance for effective web design practices. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12525-025-00777-9.