Problem in calling cross domain service using Jquery

Problem in calling cross domain service using Jquery

I am trying to call  web service (cross domain service) using Jquery.
the below working fine in IE8 , but not in chrome and firefox.
Please help me to resolve this issue. Thanks in advance
 
Test 1:
=================
    <script language ="javascript" type="text/javascript">
         function Do() {
             $.support.cors = true;           
            $.ajax({
                type: "Get",
                url: "url", // Location of the service
                data: '{"parameter"="value"}', //Data sent to server
                contentType: "application/json;charset-uf8", // content type sent to server
                dataType: "xml", //Expected data format from server
                success: function(msg) {
                    //Implement get data from service as you wish
                    alert("Success");
                },
                error: function(err) {
                    // When Service call fails
                    alert("error");
                }
            });
        }
    </script>


Test 2
==========
I am getting error, even when i try access the data from the same domain.

function Do() {
            $.support.cors = true;       
            $.ajax({
                type: "GET",
                url: "test.xml",
                dataType: "xml",
                data: "",                              
                headers: { 'Accept': 'text/xml' },
                headers: { 'Access-Control-Allow-Headers': 'application/json; charset=utf-8' },           
                error: function(xml) { alert(xml.text); },
                success: function(xml) {
                    alert("success");               
                    spnid.innerHTML = xml.text;
                }
            });
        }