2.1.2 [DOM Level 1] Section 2.4, Objects related to HTML documents

V0029:

The specification states:

 Attribute
 domain 
 The domain name of the server that served the document, or a null string if the 
 server cannot be identified by a domain name.

All Document Modes (All Versions)

An empty string is assigned to the value of the domain attribute when the local machine is the server.