The link points to seapug.org which is not the place we're currently posting meetups. We like that domain name and here in Seattle we've been talking for a couple years on ideas for doing something with it.
I get a few people a year who ping me asking if it's a mistake that the link points to the old website - had a few more pings over slack recently. Things are moving slowly and nothing is changing in the near future, so it probably makes sense to update the postgresql.org website to point to meetup.com/seattle-postgres
If we manage to do something with the seapug.org domain we can switch the link on postgresql.org back.
I've updated the link for you (though I'm sure you meant https, so I made it that :P)