JSON: Breaking the same-server-policy Ajax barrier
The same origin policy prevents document or script loaded from one origin from getting or setting properties ( XMLHttpRequest ) of a document from a different origin. The policy dates from Netscape Navigator 2.0. This is a very important security restriction which disables rogue third-party javascripts from getting information from your authenticated banking server session. Unfortunately, this also almost completely shuts down any possibility of data sharing between multiple servers. Note the use of the word "almost", because "JSON" is the new Saviour of web2.0 world. JSON or Javascript Object Notation , is nothing but a simple data interchange format which can be easily used by javascript applications. Whats different here is that unlike XMLHttpRequest which can send back answers in any format the javascript application wants, JSON requires the answers to be in JSON format, which is basically a subset of Javascript Programming language , or to be more spec