The SingleImagePlaceholderControl and SingleAttachmentPlaceholderControl have a small bug: they render a link to an image named transparent.jpg in the current directory.
As this is only a cosmetic bug that causes 404 errors in the IIS log this bug will not be fixed in a hotfix. As this is still an anoying problem for some users I have implemented two custom placeholder controls derived from the original placeholder controls which fix the problem.
Corrected Image and Attachment Placeholder Controls
Since this only occurs in edit mode, would a quick solution for this be to drop a transparent.jpg (which should be a gif anyway) into the %MCMS Install Path%\Server\exeres folder.
Because its only edit mode we should be assured that the relatively linked image would always be pulling from the NR/Exeres virtual directory correct?
By the way, looking forward to the new book. Read the first one and loved it, can't wait to see what you all come up with for this one.
might be a solution. In my templates I had a couple of postbacks and here the path also changed to the template project with template file format. So you would have to place it at least into two locations.