The site domain specifies the primary domain of the web site you want to track. For example, your site could have the primary domain yourbusiness.com as well as the subdomains electronics.yourbusiness.com and paperproducts.yourbusiness.com. You should specify the domain without the www prefix.
By default, Webtrends tracks each visitor's traffic using across all subdomains. For example, your Webtrends data will show a customer's visit to yourbusiness.com and electronics.yourbusiness.com as the same visit. If you want to track visits to yourbusiness.com, electronics.yourbusiness.com and paperproducts.yourbusiness.com
as completely separate visits, click Visitor Tracking and select the Track visitors to the primary and each sub-domain separately check box under Cookie-Based Tracking.