WT.site
WT.site=siteId
This Visitor Data Mart parameter enables the web site owner to supply a site ID for one or more events when multiple events occur on the same hit. The JavaScript tag generates and sets this parameter to the domain name/Site Id for cross-domain Visitor Data Mart use, enabling users to select only events for a certain ID when querying the database.
Currently, this parameter is not supported in Tag Builder and must be configured manually.