Here we have two gallery shortcodes. The first uses the
link=file parameter to link to the attachment file. ie. the image. When the fancybox opens a single image is shown.
The second uses
link=post to link to the attachment page. When the fancybox opens it operates as an iframe.
See also[bw_jq] [gallery] Mtrax-at-Emsworth-RHS Mtrax-at-Emsworth-LHS jQuery Fancybox
hover to slideToggle source