Cookie consent dialog
Project-GC will display a cookie consent dialog (developed by Google) when it wants to send cookies to the user. If the cookie storing information about this consent is later removed, the consent dialog will appear again. Also, you will be asked to reconfirm this periodically, every few months or so.
Other things interfering with the cookie consent dialog (and solutions)
Adblockers: Some adblockers will cause your answer to the cookie consent dialog to not get stored, causing the dialog to appear for every page view. To fix this, set your adblocker to whitelist Project-GC. If you are a paid member, whitelisting Project-GC in your adblocker is not a problem since you won't be shows ads anyway.
Disconnect plugin: With the "Disconnect" plugin present in Firefox and ABP running, a user reported having to have to turn the "Disconnect" plugin off (thus allowing Google tracking) to get the dialog to not trigger.
Kaspersky antivirus: A user reported that he had to whitelist Project-GC in Kaspersky antivirus in order to not have the antivirus trigger the dialog (Mac, Chrome).