We analyse the main functions of modern web portals that differ them from other types of sites. In this work we consider intelligent information-analytical web portals as a specific subset of intelligent information-analytical systems, and their features and development trends that have an influence on their semanticization are analysed. As a part of such analysis we considered knowledge models and technologies of their processing that can be used for this aim. We determine standards and tools of the Semantic Web that can be used for the semanticization of web portals and describe the ways of such use on practical examples. Some basic requirements for technologies and instrumental tools used for development of semantic portals are considered. We analyse and classify typical problems related to the processing, structuring, and analysis of large volumes of data that arise in the process of creating and deploying such portals, and the criteria for evaluating the development opportunities of existing web portals are considered. On example of web portal based on semantic Wiki technologies we investigate practical problems of implementation and scaling of portal knowledge processing tools and services and propose some ways of their prevention and solution.