The easiest way to find the owner or publisher of a website is to go to the WHOIS website, find the WHOIS section and search for the domain name. In the returned data, the "registrant" is the person who owns the site.
In some cases, a company such as Domains By Proxy registers a domain on behalf of the owner to keep the owner's personal information private. The best option in this case is to email the private registry company and request the information. If this fails, a court order can force the private registry company to reveal that information.
If the owner had contact information on earlier versions of the same Web page, it may be available by searching the Internet Archive.