i am asking for publish_stream permission from user when they are trying to login on my website with facebook. Now i want to post on user's wall.

i am using below code but this code require me to login on facebook and posting on my wall only, please tell me how to post on user's wall?

<html xmlns="http://www.w3.org/1999/xhtml"
    <title>My Feed Dialog Page</title>
    <div id='fb-root'></div>
    <script src='http://connect.facebook.net/en_US/all.js'></script>
    <p><a style="cursor:pointer" onclick='postToFeed(); return false;'>Post to Feed</a></p>
    <p id='msg'></p>

      FB.init({appId: "APP ID", status: true, cookie: true});

      function postToFeed() {

        // calling the API ...
        var obj = {
          method: 'feed',
          redirect_uri: 'http://mysite.com',
          link: 'http://mysite.com',
          picture: 'http://mysite/images/banner-1.png',
          name: 'Mysite',
          caption: 'website',
          description: 'website'

        function callback(response) {
          document.getElementById('msg').innerHTML = "Post ID: " + response['post_id'];

        FB.ui(obj, callback);