Why does my subscribe form have prefilled in information that is not me?

When testing subscribe forms, it is possible to see a form prefilled with another person's information. This could be due to cookie that is set in the browser with another contact's unique identifiers (MemberGUID).  

Please go through the appropriate steps to delete your browser cookies before testing the form again.

Notes

This is not the same as the browser cookies that are set for the Clicksteam integration.