I want to add a couple of good ones I’ve found:
Jeff the Killer lost media: no one knows where the original Jeff The Killer image came from.
Mortis.com: old weird website
Also here’s a good website on various obscure computer/Internet related oddities: https://suricrasia.online/iceberg/
I was recently recommended an internet mystery by YouTube. I didn’t know about it until then (and I’m generally pretty online), so it’s probably not well known.
It’s the song, Like the Wind (or Blind the Wind). Story goes that a kid recorded the song in 1984 from a West German radio station, but he didn’t catch the name of the song nor the band. Eventually, the recording got posted online, and strangely enough, nobody online seems to recognize it. It’s still unknown where this song came from. People call it Like the Wind (or Blind the Wind) because that’s what the first 3 words of the song sound like. Speculation is that it’s probably from an East German indie rock band that got disbanded, but at this time, it’ll probably never be solved
Got wrapped up into that a while back, an interesting tangent is the song So Do I by DCO, which was similarly lost until one of the band’s original members recognized it and posted it online. Said member did confirm that TMMS/Like The Wind is not a song they made, tho.
Just like everybody knows https://youtu.be/ZmTcIh632VM?si=yDNEMk09wk-mX-et