[Zope] transparent gifs

I've been attempting to use a 'spacer.gif' but run into problems with Zope's rendering of it. Specifically, the space that should be transparent is instead gray. When viewed from the ZMI, it is transparent. When called from a page template, as with the following code, it is not. Likewise, it is gray when called from the web directly. <img src="spacer_gif" width="30" tal:attributes="src here/images/spacer_gif/absolute_url" > http://localhost:8080/images/spacer_gif Thanks for reading, Danny