We assign a certain rating to our publishers' websites ranging from 0 to 1. 0 is the lowest quality, 1 is the highest quality. Since 1 is near perfect by our definition, you should avoid targeting websites at this range. If you want to get high quality traffic/impressions your safe bet will be above 0.5. Mind that less than 20% of our ad units satisfy this criteria, which means that this quality range may increase the price of the traffic significantly.