To prevent this from taking place you will need to add the Munchkin Initialization Parameter setting the “domainLevel” to “2”. This will cause the cookie to be set to the second domain level “example.co” when visiting either the Marketo or non-Marketo hosted landing pages. Details about the Munchkin Initialization Parameters can be found in this Developers Doc:
http://developers.marketo.com/javascript-api/lead-tracking/configuration/#domainlevel_property
Since the Marketo hosted landing pages will, by default, use the same 3 third level domain behavior, you will need to disable tracking at your template level using the steps at the end of this article:
http://docs.marketo.com/display/public/DOCS/Create+a+Free-form+Landing+Page+Template
This will disable the default tracking that all landing pages get in Marketo. Then, similar to external landing pages, your team will need to add the Munchkin tracking code to your Marketo templates, where you would have control to set the domain level to 2 (instead of 3). Once this has been updated on both the external landing pages and Marketo hosted landing pages, the tracking cookies will be set at the second domain level and work across the various sub-domains.
Who This Solution Applies To
Customers with two letter domains