How to set custom thumbnail for facebook link of your page

sometime facebook can not fetch your image in your page. to add image to your link you can use :

<link rel="image_src" href="http://media.clickonf5.org/image/logo.png" />

facebook will cache the facebook pages, if you want to refresh the cache you can add some parameter to your page like mypage.html?t=! or using URL Linter

URL Linter
http://developers.facebook.com/tools/lint/

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