facebook Send Button pick up default image from site how to change this image according to our us?

when you use Facebook's Send button its shows which images and how to change this image

 

 

 

1st thing you have to do is:
follow this link

 

http://developers.facebook.com/tools/debug

enter the url and check the Object Properties and see the title image and description , image of facebook page. now go to header of your website and and set top of the page title , description, keywords, image

for image you can paste this code and change the path of website
<meta name="image" content="http://www.earlyshares.com/public/images/earlyshares-petition.png" src="http://www.earlyshares.com/public/images/earlyshares-petition.png"/>

change the image name according to website which one you want to show in below the facebook send button 

please clear the cache and cookie before to test this.
  and confirm that meta image code should be top from the send button