Here I share what I did to post to the fb wall. This way you do not need to use appId. Just put this code on your HTML page wherever you want the link to it ...
<a name="fb_share" type="button" href="http://www.facebook.com/sharer.php?u={$url}&media={$imgPath}&description={$desc}" class="joinFB">Share Your Advertise</a>
URL parameters are shown below.
u: URL or link that you want the user to be able to go when he clicks on your message on the wall,
media: the full path to the image, make sure that the image is accessible at the specified path, it will only accept one image
description: a brief description that you want to show on the wall

He will also ask you to write some data that will be displayed above your message. The description passed in url will be displayed on the right side of your image.
Please note that I passed the variables $ url, $ desc, $ imgPath according to my need. The above code is in smarty-php, so change it as per your requirement.
Hope this helps you.
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