Conversion Tracking Cookie Expiration
Navigation (for Account Administrators
only): Select 
Account on the side navigation bar. Select Campaign management, and then select Conversion tracking settings. (Not seeing this choice? Refer to the Account management changes topic.)
Conversion tracking processing requires that your email recipient's browser is set to accept cookies. A recipient can also prevent a conversion from being recorded by clearing cookies between clicking the tracked link (when the cookie is written to the recipient’s system, and visiting the conversion page (when the cookie is used to record a conversion).
The Account administrator may use this page to enter the number of days after which your conversion tracking cookie for the associated campaign will expire.