Android : Http 400 error coe in Hiting Api in android the URL is " http://khanhzpz.vn/CRM/modules/Mobile/api.php"

I wants to hit this link in for login in http://khanhzpz.vn/CRM/modules/Mobile this site but every time it returns the HTTP 400 error code. if i hit this website url("http://khanhzpz.vn/") only then also it shows same error.

i also used the REST Api Library,Normal HTTP hit,Volley Library. please help me out .. Here is my Function to hit api.

 public void postData() {
    try {
        String url = "http://khanhzpz.vn/CRM/modules/Mobile/";
        HttpClient httpclient = new DefaultHttpClient();
        HttpResponse response = httpclient.execute(new HttpGet(url));
        StatusLine statusLine = response.getStatusLine();

        AndroidHttpClient httpClient = AndroidHttpClient
                .newInstance("User Agent");

        // String url = "http://khanhzpz.vn/CRM/modules/Mobile/";
        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
        nameValuePairs.add(new BasicNameValuePair("username", "sarbjot"));
        nameValuePairs.add(new BasicNameValuePair("password", "1235"));
        URL urlObj = new URL(url);
        HttpHost host = new HttpHost(urlObj.getHost(), urlObj.getPort(),
                urlObj.getProtocol());
        AuthScope scope = new AuthScope(urlObj.getHost(), urlObj.getPort());
        HttpContext credContext = new BasicHttpContext();
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

        // Execute post request and get http response
        HttpResponse httpResponse = httpClient.execute(host, httpPost,
                credContext);
        String responseBody = EntityUtils
                .toString(httpResponse.getEntity());
        System.out.println("response :" + responseBody);
        httpClient.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

}

if i hit facebook.com it returns sucess 200 ok statusLine.

thanks in advance.