Web sites that include 3D content, i.e. Web sites where users navigate and interact (at least partially) through a 3D graphical interface, are increasingly employed in different domains, such as tutoring and training, tourism, e-commerce and scientific visualization. However, while a substantial body of literature and software tools is available about making 2D Web sites adaptive, very little has been published on the problem of personalizing 3D Web content and interaction. In this paper, we describe how we are exploiting a recently proposed 3D Web technology, i.e. the X3D (eXtensible 3D) language, for adaptive manipulation of 3D Web content.