@khurshid-alam sorry for the inconvenience. They were dropped because of technical complications on the server they were hosted on, but If there is enough interest, we can look into hosting them again. Note that these docs are also available locally in the relevant *-doc deb packages, such as libunity-api-doc.
For the time being, I’ve created a GitHub repo with the content you are looking for.
Our next step is setting up redirects on the developer portal to point to this repo.