problem in ajax

i am using the below code to initialize the xmlhttprequest

try
{
obj = new XmlHttpRequest();
}
catch(e)
{
try
{
obj = new ActiveXObject("Microsoft.XMLHTTP");
}
catch(e1)
{
obj = new ActiveXObject("Msxml2.XMLHTTP");
}
}

 it works fine in my system. but when accessed from network, the ajax features
doesnt work. I have placed the code for ajax and some validation
scripts in the .js file. The validation scripts works fine, but not the
ajax scripts.
Please give me solution...Its urgent.

try this url

http://www.scss.com.au/family/andrew/webdesign/xmlhttprequest/

This will help you to create a XmlHttpRequest Object which is supported by all browsers.