The rust-ci.org domain appears to have expired and redirects to random pages, mostly ads. I had several old crates that I had forgotten were using rust-CI to host their docs and now their docs links are bogus.
If memory serves, it was implied that Rust-CI was not going to be able to operate forever; I think it was hosted on one person's machine from their home. On behalf of the community, I would like to thank the original operator of Rust-CI for their service, though I have unfortunately forgotten their name.
Most of us know about docs.rs already. It is run by a team of volunteers and graciously hosted by leaseweb as detailed on the About page. Like Rust-CI, there is no setup necessary to use Docs.rs; if your crate is published on Crates.io, its documentation (built with the default features) is already available under https://docs.rs/<crate>. Crates.fyi is also redirecting to Docs.rs.