Jquery Ajax Setting

$.ajax({
    beforeSend: function(req) {
        req.setRequestHeader("Accept", "text/xml");
    },
    type: "GET",
    url: "[proper url]",
    contentType: "text/plain; charset=utf-8",
    dataType: ($.browser.msie) ? "text" : "xml",
    username: '---',
    password: '-------',                                
    success: function(data) {
        var xml;
        if (typeof data == "string") {
            alert("Data is string:" + data);
            xml = new ActiveXObject("Microsoft.XMLDOM");
            xml.async = false;
            xml.loadXML(data);
        } else {
            xml = data;
            alert("Data is not string:" + $(xml).text());
        }
        // Returned data available in object "xml"
        //alert("Status is: " + xml.statusText);
        $("#ingest_history").html($(xml).text());
    }              
}); 

If you never view this kind of setting than this is time for you read this article  why set this setting ? ans is here : 

beforeSend :    A pre-request callback function that can be used to modify the jqXHR (in jQuery 1.4.x, XMLHTTPRequest) object before it is sent. Use this to set custom headers.  

 Type :    "get" or "post" set HTTPRequest type.if u set "get" than ur data is view in url.so my advice  is use "Post" 

contentType:  if you set contentType to plain/text than your result allways accept plain/text    

dataType:   what kind of data you want ? xml , html ,text  

  success:   call user define function if your ajax request successfully executed