XmlHttpRequest object,how should I use?
XMLHttpRequest object is a kind of web client that can retrieve and submit XML data directly then convert retrieved XML data into HTML content.

 XMLHttpRequest object is supported in almost browser providers:

- Microsoft,it works as an ActiveX and is supported in Internet Explorer 5.0 or later as an  
  ActiveX object

- Mozilla,in Firefox1.0 or later

-  Apple,in Safari1.2 or later

How to create?
Currently,there are two ways to create object based on the browser provider:

 For Microsoft:

Var oXMLRequest = new ActiveXObject(“Microsoft.XMLHTTP”);

 For Mozilla and Safari

 Var oXMLRequest = new XMLHttpRequest();