https://docs.fedoraproject.org/en-US/Fedora/23/html/Installation_Guide/ix01.html The Index contains a single entry (Feedback). It seems like the Index needs to be removed, maybe it was accidentally created by some annotation made on the Feedback section. (I looked at Index because there wasn't an obvious search function).
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.