Since the sole purpose of ATOL is to work with ad content, you should be sure that you do not have an Ad Blocker installed. Therefore, it does not make sense to leave your Ad Blocker enabled. Otherwise, the Ad Blocker will intentionally block digital advertisements. This will make all your ad proofs appear blank and the site will not work properly.
The most popular Ad Blocker is Adblock Plus. It has plug-ins for Google Chrome, Mozilla Firefox, and Opera.
You can click on the arrow of the Adblock Plus icon in the toolbar to bring up the menu. There you have the option to disable/reenable Adblock Plus.
If you've disabled Ad Blocking, you're ready to jump to "Logging in".