It must be designed to catch the eye and allow visitors to explore freely. Remember that one of the defining characteristics of a portal is its emphasis on services for members of the community. If the primary web page were so restricted, it would loose some of its usefulness as a marketing tool. Organized by internal structures and concepts. Sometimes provide keywords and indexes.
Primary audience is external to the institution.
Often characterized by little control over presentation or design. Include categories of information not based on organizational structure such as News, Directories, Calendars. Incorporate something that changes like regularly updated features such as News or daily events calendars. Incorporate search capabilities to augment the navigation design. Primary audience is external to the institution.