Pinit Share not working

i jus added a pinit share button to pin my images in posts . Here is the URL .

<!--Pin It-->
    <a href="http://pinterest.com/pin/create/button/?url=<?php the_permalink(); ?>"     class="pinit" title="Share this post on Pinterset!" target="_blank"></a>  

And when i click on it it leads me to pinit site . and when i click pinit it shows the following error

You need to upload an image or provide the ‘image_url’ parameter

i dont know what wrong i have done. Please help!! thanks !!