AJAX allows web pages to load data or markup fragments from a server using asynchronous requests that are processed in the background and thus do not interfere with the web page that is currently displayed in the browser. When you use AJAX, your Web application exchanges only small amounts of data between the server and the client and consequently refreshes small parts of the markup only. Therefore AJAX is also useful for building mashups that are aggregating content from various different sources into a uniform user experience. For example, this can be RSS or Atom feeds or other data retrieved from external REST services.
The solution that Mashup Center offers is based on a server-side HTTP proxy, called the HTTP Proxy for AJAX Applications (also known as the Ajax Proxy). The underlying security model allows administrators to restrict access to trusted origins in a very flexible way.
Parent topic: Configuring security