Description of problem: * `ks=https://git.fedorahosted.org/cgit/spin-kickstarts.git/plain/fedora-install-server.ks?h=f21` is in the uefi cmdline for Server. f21 should read f25. * `append f25/initrd=initrd.img` is under the uefi rescue configuration. It should probably read `append initrd=f25/initrd.img`. * inconsistent use of `linuxefi` vs `kernel`. In the section for the installation of Fedora server, it uses `kernel`, whereas for Workstation, it uses `linuxefi`. One of these is almost certainly an error. Additional info: Errors found on f25 page (https://docs.fedoraproject.org/en-US/Fedora/25/html/Installation_Guide/pxe-bootloader.html)
#1 actually looks like it isn't a problem, though it certainly is confusing to be using an f21 branch for f25 installation.
Typo in BIOS config: `append initrd=f25initrd.img ip=dhcp` should read `append initrd=f25/initrd.img ip=dhcp`
The install guide has been retired, therefore I'm closing this bug. If you would like to report Fedora docs bugs in the future, please use the "bug" icon on the top right of the affected page, it will take you directly to the appropriate issue tracker.