The variable is used to identify the domain with which cookies are set.
Analytics uses a cookie to uniquely identify visitors to your site. If visitorNamespace is not used, the cookie is associated 2o7.net. If visitorNamespace is used, the cookie is associated with a sub-domain of 2o7.net. All visitors to your site should have their cookies associated with the same domain or sub-domain.
The reason for using the visitorNamespace variable is to avoid the possibility of overloading a browser's cookie limit. Internet Explorer imposes a limit of 20 cookies per domain. By using the visitorNamespace variable, other companies' Analytics cookies will not conflict with your visitors' cookies.
Syntax and Possible Values
The value of visitorNamespace must be provided by Adobe and is a string of ASCII characters that don't contain commas, periods, spaces, or special characters.
Visitor Identification across Report Suites
If you do not specify a visitorNamespace , each report suite in your company receives its own visitor ID cookie written as s_vi_[random string] . If you specify visitorNamespace , the same s_vi cookie will be used for all report suites that send data to the specified trackingServer . If you have implemented multi-suite tagging, make sure you specify the visitor namespace so the same cookie is used by each report suite.