After running make I attempt to run mapserv as in http://mapserver.gis.umn.edu/doc36/unix-install-howto.html and I am given the error "./mapserv: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory" libpng12.so.0 exists because libpng has been installed. Any suggestions on how to correct this problem? Seamus