Surely you've seen a red screen in your browser warning you of a dangerous website. It appears when you try to enter websites that are on the Google blacklist. RBL, on the other hand, is a blacklist of domains associated with spam.nYou don't want your website to appear on either of these lists. But if it does happen, you need to find out about it as soon as possible to clarify the matter and arrange to have your domain removed from such a list.