As you administer servers, you will begin to spend a lot of time on the command line. Most likely, you will be using the bash shell. The bash shell includes a lot of commands and expansion capabilities to take advantage of the input you have typed in
In case anyone else comes along, I had the same problem using Apache 2.4.6 (Ubuntu). It had to do with apache not having permission to /usr/lib/iipimage-server. I simply copied that to /usr/share/iipimage-server and adjusted the path in iipsrv.conf and the url worked.