Difference between vs development server and IIS Server

Question

I am develop a website,which using PageMethods, in vs development server, it can fire, but not in local iis server（got 500 error and timeout in firebug）,how do i debug? this is a popup window, in call, i get the parent window's url,use pagemethod to get calling number by url, the fire call.

<script type="text/javascript">
    function call() {
        var location = null;
        if (window.opener != null) {
            location = window.opener.location.href;
        }
        else {
            location = "-1";
        }
        var called = document.getElementById('<%=txtCalled.ClientID%>').value;
        location = location + "|" + called;
        alert(location);
        PageMethods.StartCall(location, onSucess, FindResultTimeout, FindResultError, null, 10000);
    }

    function onSucess(phone) {
        alert(phone);
    }

    function FindResultTimeout() {
        alert('timeout');
    }
    function FindResultError(result, response) {
        alert(response.get_statusCode());
    }

</script>

call mehtod:

 <a href="javascript:call();">call</a>

codebehind method:

[WebMethod]
    public static string StartCall(string referer)
    {
        var paras = referer.Split('|');
        string calling = GetNumberByDomain(paras[0]);
        addLog(paras[0], paras[1]);
        return clickToDial(calling, paras[1]);
    }