A web portal is a site that provides a single function via a web page or site. Web portals often function as a point of access to information on the World Wide Web. Portals present information from diverse sources in a unified manner. Aside from the search engine standard, web portals offer other services such as e-mail, news, stock prices, infotainment and various other features. Portals provide a way for enterprises to provide a consistent look and feel with access control and procedures for multiple applications, which otherwise would have been different entities altogether. An example of a web portal is Yahoo!
Two broad categorization of portals are a. Horizontal portals (e.g. Yahoo) b. Vertical portals (focused on one functional area. e.g., salesforce.com)
A personal portal is a site on the World Wide Web that typically provides personalized capabilities to its visitors, providing a pathway to other content. It is designed to use distributed applications, different numbers and types of middleware and hardware to provide services from a number of different sources. In addition, business portals are designed to share collaboration in workplaces. A further business-driven requirement of portals is that the content be able to work on multiple platforms such as personal computers, personal digital assistants (PDAs), and cell phones/mobile phones.
A personal or web portal can be integrated with many forum systems.
In the late 1990s, the web portal was a hot commodity. After the proliferation of web browsers in the mid-1990s, many companies tried to build or acquire a portal, to have a piece of the Internet market. The web portal gained special attention because it was, for many users, the starting point of their web browser. Many of the portals started initially as either web directories (notably Yahoo!) and/or search engines (Excite, Lycos, AltaVista, infoseek, Hotbot, and Itsabove among the old ones). Expanding services was a strategy to secure the user-base and lengthen the time a user stayed on the portal. Services which require user registration such as free email, customization features, and chatrooms were considered to enhance repeat use of the portal. Game, chat, email, news, and other services also tend to make users stay longer, thereby increasing the advertising revenue.
Web Portal Development 
is undertaken by Indian web marketing firms and they have been doing a very food job of it. In fact they have incorporated new and newer technologies in this field and have become very good experts in this field. They are rated as top web portal developers.