Check whether a file you have is byte-for-byte the same as one published on albertlane.net. Your file is hashed (SHA-256) in your browser and is never uploaded. The page compares that fingerprint with the published list in /site-directory.json.
PDFs and images are served unmodified, so a downloaded copy matches. For web pages (marked "page"), the fingerprint is of the source file; the copy your browser saves will not match, because the delivery network adds a small script.