■

<a href="#" onclick="Element.hide('thumbnail_photo_53559930'); Element.show('highres_photo_53559929'); return false;">

<a href="#" onclick="Element.show('thumbnail_photo_53559929'); Element.hide('highres_photo_53559929'); return false;">

このふたつでトグルしとるのね。Element.show, Element.hideっていうのがどこから来てるかわちょっと置いておこう。prototypeとかいうのらしいけど。

<a href="#" onclick="Element.hide('thumbnail_photo_53559930'); Element.show('highres_photo_53559929'); return false;">
	<img class="image_thumbnail" alt="" id="thumbnail_photo_53559929" width="100" height="77" src="http://media.tumblr.com/H0D6rv0NTesykvjikvIx0uP7o1_100.png"/>
</a>

<div id="highres_photo_53559929" style="display:none; margin-bottom:20px;">

	<a href="#" onclick="Element.show('thumbnail_photo_53559929'); Element.hide('highres_photo_53559929'); return false;">
		<img class="image" alt="" width="500" height="383" src="http://media.tumblr.com/H0D6rv0NTesykvjikvIx0uP7o1_500.png"/>
	</a>
	<div style="font-size:10px;">
		<a href="http://muxtape.com/remembers/taizooo">muxtape.com</a> &#8594;
    </div>
</div>
                            
<div class="caption" style="margin-top:0px;">
	<a href="http://muxtape.com/remembers/taizooo">Muxtape remembers taizooo</a>
</div>

http://www.tumblr.com/show/everything/by/me/2