Pretty much everything about the early days of the web.
Things came and went and no one kept track of it, probably because it wasn't possible to keep track of it. There's no trace of the company that I first rented web server space from back in 1995, no mention of them anywhere, no mention of the provider that I used to get on the Internet, things like that. Just about every time I've tried to find information about anything related to the mid-90s web, I've hit a brick wall.
The "Way Back Machine" at archive.org is supposed to be the history of the web, but it doesn't go all the way back, and most of the older stuff they have is so broken it's pretty much worthless. Their copies don't support technologies that were commonly used back in the day, like image maps, and many kinds of "active" pages. Consequently it's just weird little fragments.
This guy is the only one to come close to producing a history of the early web (ostensibly he starts that history with Netscape, but in the course of the interviews they often go back further). He's doing a good, thorough job, but he only started his podcast a few years ago. Before that, the things he's talking about - you couldn't find anything about them.