Java unknown host exception

I am trying to access textalertapp.com via HTTP Post request from my android application. But I am getting Unknown host error. Can anybody help me solve this issue.

12-13 01:30:16.058: WARN/System.err(473): java.net.UnknownHostException: textalertapp.com

    12-13 01:30:16.088: WARN/System.err(473):     at java.net.InetAddress.lookupHostByName(InetAddress.java:513)

    12-13 01:30:16.088: WARN/System.err(473):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:278)

    12-13 01:30:16.088: WARN/System.err(473):     at java.net.InetAddress.getAllByName(InetAddress.java:242)

    12-13 01:30:16.088: WARN/System.err(473):     at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:136)

    12-13 01:30:16.099: WARN/System.err(473):     at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)

    12-13 01:30:16.099: WARN/System.err(473):     at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)

    12-13 01:30:16.099: WARN/System.err(473):     at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:348)

    12-13 01:30:16.108: WARN/System.err(473):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)

    12-13 01:30:16.118: WARN/System.err(473):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)

    12-13 01:30:16.118: WARN/System.err(473):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)

    12-13 01:30:16.118: WARN/System.err(473):     at com.textalert.alertCollection.getAlerts(alertCollection.java:46)

    12-13 01:30:16.118: WARN/System.err(473):     at com.textalert.alertsList$1.run(alertsList.java:81)

    12-13 01:30:16.128: WARN/System.err(473):     at java.lang.Thread.run(Thread.java:1096)

Code is

HttpClient client = new DefaultHttpClient();

                String postURL = "http://textalertapp.com/androidCode/?api=AlertManager&method=getAlerts";

                HttpPost post = new HttpPost(postURL); 



                List<NameValuePair> params = new ArrayList<NameValuePair>();

                params.add(new BasicNameValuePair("user", "kris"));

                params.add(new BasicNameValuePair("pass", "xyz"));

                UrlEncodedFormEntity ent = new UrlEncodedFormEntity(params,HTTP.UTF_8);

                post.setEntity(ent);

                HttpResponse responsePOST = client.execute(post);  

                HttpEntity resEntity = responsePOST.getEntity();  

                if (resEntity != null) {    

                    Log.i("RESPONSE",EntityUtils.toString(resEntity));

                }

Source: Tips4all