Web sites rely on pictures and animation to convey subtle messages that are more effectively communicated nonverbally. We argue that such messages could have strong cultural content, which should be understood in developing Web sites. Hence, this paper explores the cultural content of Web site images and develops a theory for Web-image signifiers. This is done in two phases. Phase I has an interpretive qualitative approach that uses Grounded Theory to identify signifiers and to develop the Web-image signifiers (WIS) theory. Phase II quantitatively tests the WIS theory. Together, these two phases identify and validate signifiers of cultural dimensions in Web site images. More interestingly, the results uncover that cultural dimensions are signified in five categories, of which two, humans and buildings categories, are the most prominent. The contribution of this paper is in developing a comprehensive theory for the cultural content of Web images, identifying 48 signifiers in Web images, discovering new categories of signifiers, and providing insights into the nature of cultural signification by testing the theory. Such knowledge could heighten our sensitivity and awareness of hidden cultural messages in Web site images. The WIS theory could provide a novel approach to the cultural studies of Web images and other artifacts with cultural content. The results of this work have immediate application in the design of Web sites for a multicultural audience.