Failed to load resource: the server responded with a status of 400 (Bad Request)

Hi all

I am using this code to retrieve some records from businessunit

function retrive(){
var oDataEndpointUrl = serverUrl + "/XRMServices/2011/OrganizationData.svc/";
var query = "BusinessUnitSet?$select=address1_line1";

oDataEndpointUrl += query;
var contactRequest = new XMLHttpRequest();

//contactRequest.open("GET", ODataPath + "/ContactSet(guid'" + contactId + "')", false);
contactRequest.open("GET", oDataEndpointUrl, false);
contactRequest.setRequestHeader("Accept", "application/json");
contactRequest.setRequestHeader("Content-Type", "application/json; charset=utf-8");

contactRequest.send();
if(contactRequest.status == 200)
{

var retrievedTemplate = JSON.parse(contactRequest.responseText).d;
var retrievedTemplateRecord = retrievedTemplate.results[0];

}
else
{
//console.log('request failed.');
//Xrm.Page.getAttribute('cobalt_contactsemail').setValue("---No Contact Found---");
}
}

and it is giving me this error:

Failed to load resource: the server responded with a status of 400 (Bad Request)

Where may I wrong? please tell me

Thank You