The following error message might appear on a page if a subscription form control has been added to the presentation components of the corresponding content item:
Parser Error
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.
Parser Error Message: Could not load type 'Sitecore.Modules.EmailCampaign.Layouts.SubscriptionForm'.
The error is caused by a missing type definition in the Sitecore.EmailCampaign.dll assembly.
This issue affects EXM 3.1.
To resolve the issue, download and copy the Sitecore.Support.66428.dll assembly to the /bin folder.