Recently, Web-page browsing opportunities at multimodal browsing sizes have increased due to developments of various terminals. Meanwhile, most Web pages have been designed to fit to the standard size. As a result, the screen scroll operation is necessary to access the main content at a small size, whereas the blank space becomes large at a large size. In this paper, we propose a Web-page layout optimization method for multimodal browsing sizes by focusing on the standard Web design style with the separation of the document structure description by an XHTML file and the appearance description by a CSS file. Our method automatically generates a set of CSS files fit to different sizes from the files designed for the standard size by a user. Then, it dynamically switches to the CSS file fit to the current browsing size using JavaScript. We confirm the practicality of our proposal through experiments of the Web page generation and access at various sizes. ©2009 IEEE.