help on creating of record using js.

created a form using html .. what i am doing is that on submit of button I want to pass these values to another custom entity (that I created named as new_forcalllog) to create a record...

Code I written is:

function submit() {
debugger;
alert("submit");
var x = document.getElementById("mySelect").selectedIndex;
alert(x);
var y = document.getElementById("mySelect").options;
alert(y);
var z = y[x].text;
alert(z);
if (z != null) {
alert("Inside z");
if (z == "Phone")
{ var zp = 1; }
else if (z == "Fax")
{ var zp = 2 }
else if (z == "Email")
{ var zp = 3; }
else if (z == "Linkedin")
{ var zp = 7; }
else if (z == "Chat(Skype/AOL/Yahoo/MSN)")
{ var zp = 6; }
}
alert(zp);

var a = document.getElementById("mySelected").selectedIndex;
alert(a);
var b = document.getElementById("mySelected").options;
alert(b);
var c = b[a].text;
alert(c);
if (c != null) {
alert("Inside c");
if (c == "Assigned")
{ var ca = 1; }
else if (c == "Follow Up")
{ var ca = 2 }
else if (c == "Warm Lead")
{ var ca = 3; }
else if (c == "Hot Lead")
{ var ca = 4; }
else if (c == "Client")
{ var ca = 5; }
}
alert(ca);
var comm = document.getElementById("TextArea1").value;

alert(comm);
var ids = document.getElementById("TextArea2").value;
alert(ids);

var CRMObject = new Object();
CRMObject.new_contactmethod = zp;
alert(CRMObject.new_contactmethod);
CRMObject.new_new_accountstatus = ca;
alert(CRMObject.new_new_accountstatus);
CRMObject.new_comments = comm;
alert(CRMObject.new_comments);
CRMObject.new_leadids = ids;
alert(CRMObject.new_leadids);

var jsonEntity = window.JSON.stringify(CRMObject);

alert(jsonEntity);

var createAccountReq = new XMLHttpRequest();
alert("createAccount1");
createAccountReq.open("POST", "https://crmdev2015"+"/XRMServices/2011/OrganizationData.svc/new_forcalllogSet", true);

createAccountReq.withCredentials = true;
createAccountReq.setRequestHeader("Accept", "application/json");
createAccountReq.setRequestHeader("Content-Type", "application/json; charset=utf-8");


createAccountReq.onreadystatechange = function () {

createAccountReqCallBack(this);

};

createAccountReq.send(jsonEntity);

function createAccountReqCallBack(createAccountReq) {
if (createAccountReq.readyState == 4 /* complete */) {
alert(createAccountReq.readyState);
alert(createAccountReq.onreadystatechange);
createAccountReq.onreadystatechange = null; //avoids memory leaks
if (createAccountReq.status == 201) {
//Success
var newcalllog = JSON.parse(createAccountReq.responseText).d;
alert("done");
}
else {
//Failure
errorHandler(createAccountReq);
}
}
}

}

Error :   

    I am getting status 500 (instead of 201) when I am using POST and 405 status when I am using PUT...

If anyone have some idea please give might be helpful!!

Thanks!!