In the event that a respondent incorrectly types a survey link in to their browser or perhaps does not copy and paste the entire survey link into the browser, a Survey Not Found Page will be displayed.
If you have set up a Private Domain you have the option of specifying a custom Survey Not Found Page. To set this up edit your private domain and insert a URL here in the Survey Not Found URL field.
The Survey-Not-Found Page displays in the event that a survey link is incorrect (perhaps manually typed incorrectly or improperly copied/pasted) or does not exist. If your survey link is http://pdtest.com/s3/MySurvey and a respondent types in http://pdtest.com/s3/My (missing the last part of the link), the Survey Not Found Page would be displayed.
If the respondent simply uses pdtest.com, unfortunately the Survey Not Found Page would not be displayed as the /s3/ portion of the link tells SurveyGizmo to look for a survey.
If a Survey Not Found Page is not specified, the default SurveyGizmo Survey Not Found Page will be displayed.