Javascript question: change SRC value of IMG

I am trying to change an IMG tag's SRC value when a button gets clicked. The button is on an iFrame and the IMG tag is on the TOP Document.

Thank you in advance!

My button HTML:
<a href="javascript:void(0)" class="add_featured_btn button-secondary" rel="<?php echo $attach_id;?>">Use as gift image</a>

My IMG HTML:
<img id="hm_uploaded_giftimage" src="" alt="Your Gift" />

I've tried this javascript:::

<script type="text/javascript">
$(".add_featured_btn").click(function(){
$("img#hm_uploaded_giftimage",top.document).attr({ src: 'http://www.ourhoneymoongiftregistry.com/wp-content/uploads/2012/02/IMG_75102-150x150.jpg'});
});
</script>

I've also tried this javascript::::

echo "<script type=\"text/javascript\">
		jQuery(\".add_featured_btn\").click(function(){
		jQuery(\"hm_uploaded_giftimage\",top.document).setAttribute('src', '". $img_preview . ";');
		});
		</script>";