https://admin.fedoraproject.org/pkgdb/builds/show/F-17-x86_64/libpng-comp...
both download links are 404ed....it appears the folder linked to:
http://dl.fedoraproject.org/pub/fedora/linux/development/17/i386/*
./development/17 nolonger exists, believe its under ./releases
have a happy new year!