How to add facebook share button on my website?

I have this code that suppose to work, but doesn't work.

<script src='http://connect.facebook.net/en_US/all.js'></script>
    <p><a onclick='postToFeed(); return false;'><img src="images/fb.png" /></a></p>
    <p id='msg'></p>

    <script> 
      FB.init({appId: "338334836292077", status: true, cookie: 

true});

      function postToFeed() {

        // calling the API ...
        var obj = {
          method: 'feed',
          redirect_uri:'https://www.facebook.com/cryswashington?fref=ts',
          link:'https://developers.facebook.com/docs/reference/dialogs/',
          picture: 'http://fbrell.com/f8.jpg',
          name: 'Facebook Dialogs',
          caption: 'Reference Documentation',
          description: 'Using Dialogs to interact with users.'
        };

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

        FB.ui(obj, callback);
      }
    
    </script>

I want to add facebook share button on my website, that should just post my website's content on the wall. Can anyone help me?

You don't need all that code. All you need are the following lines:

<a href="https://www.facebook.com/sharer/sharer.php?u=example.org" target="_blank">
  Share on Facebook
</a>

Documentation can be found at https://developers.facebook.com/docs/reference/plugins/share-links/