Currently, the URL for source code examples listed on Cmake Tutorial gives a 404 according to wget. Trying to access the URL with FireFox does nothing except open up a blank page.
Without the example code much of the tutorial is not able to be followed.
The link works for me.
I suspect that you happened to be viewing the “latest” URL view of the 3.23 documentation page around the time we updated it to the 3.24 documentation. Taking the URL you posted and replacing /latest/ with /v3.23/ produces a working link. Viewing the latest view of the tutorial now links to 3.24’s source archive.