A method and system for rendering dynamic web page images on a display is disclosed. Code is encapsulated in an external behavior component for affecting the behavior of elements inserted into an HTML document. A simple reference is attached to the element in the document to associate the element with the external behavior component. When the document is provided to a renderer and the renderer parses the element in the document, the renderer accesses the external component to modify a behavior of the page image. Multiple documents can reuse external behavior components, and an element can be associated with multiple external behavior components. The associations between elements and external behavior components may be maintained in cascading style sheets, inline with the elements, and in various formats.