I guess we're talking WWW or Web 2.0 or HTTP(S) or whatever (ie. bloat). Cu2 was a Dutch predecessor of Hyves which were both a very popular social network in The Netherlands before the existence of MySpace and Facebook. Eventually, "everyone" went to Facebook though.
Both were colorful (think: IRC on DALnet, or MySpace). It was awful.
The thing is, social networks existed before the term was ever coined. They were just called your "network". Getting to know people was called "networking". And most people get a job through their "network". It is nothing new. Something like Usenet or IRC or a MUD just as well fits.
Ah CU2, the memories. It's a while ago. One of the interesting things there is that it actually made people aware of technology. You had to learn some HTML (for horrible purposes though), you had to read urls.
Maybe it wasn't always for the good (eye bleeding color schemes for example). But I'm sure a lot of people learned the basics of HTMl through those types of websites.
A friend of mine knew the guy (one of the guys?) who was creating Cu2 at the time and we as nerds were laughing at it like: "You can't be serious, who would want to use this?!".
Same with startpagina.nl, a really basic portal that eventually was sold for a lot of money.
Or as Bill Hicks used to say: "Boy, do I NOT have my finger on the pulse of America."
I (barely) recall chain letters being a very common thing back in those days. Probably the first form of "viral content" on the internet. Reading that email, it's easy to connect the dots of how sixdegrees probably had the idea of capturing that viral nature in a web app. Great example of clever and somewhat successful adaptation.
In the UK, before Facebook we had Friends Reunited which many, many people were members of. It seemed to pass a number of hands after the original developers sold it - ITV bought it but it was beginning to lose members and interest, and they eventually sold it on to someone else. I reconnected with one of my old best friends from school who I'd not seen or spoken to in about 15 years so I certainly have it to thank for that (and we're still in touch).
There was another social media/networking site called Faceparty that was a little closer to Facebook and I used that for a short while before eventually going on to MySpace and then Facebook. And now I've dropped social media entirely - don't miss it in the slightest.
It's a pretty awful name but it was around well before Facebook appeared or certainly became popular, I used it for a short while around 2002-2003. It wasn't a great place and I'm amazed it's still online.
I spent way too much time on undernet during the same period of time, mostly on #asp. I got my first and second programming jobs through friends I made there.
Wasn't there a site ran by one of the #html ops, htmlcenter or something like that?
I recall sixdegrees. I was invited to it by the same person who got me to sign up classmates.com and Friendster.
As far as websites with useful social networking functionality that resembles what we have today, I would say the PHPbb/vBulletin style forums were there early on. Sometime around 1999, I joined a forum on ezboard.com(1) which ended up turning into a long running discussion and meeting site. It was moved to a private server after ezboard transitioned in some way and deleted everyone's content circa 2003. It was the most prominent online resource in our artist community until it was replaced by Facebook and then Instagram.
In 1998 here in Sweden kids were joining the Skunk network, a very early social network. I guess it sort of exploded around that time so it's hard to backup a statement like "the first online social network".
I remember getting that email from a friend (who's still my friend) and thinking nah. Same with friendster which existed pre-MySpace. Folks comparing this to MOOs and IRC are missing that this was one of those first anglings to do what MySpace and Facebook eventually did. IRC and other online environs weren't built to gather users and use their information as raw material for advertisers. Sixdegrees was, it just failed earlier and faster than most.
Both were colorful (think: IRC on DALnet, or MySpace). It was awful.
The thing is, social networks existed before the term was ever coined. They were just called your "network". Getting to know people was called "networking". And most people get a job through their "network". It is nothing new. Something like Usenet or IRC or a MUD just as well fits.