Over a year ago, Microsoft adCenter launched a quality ranking component to their search ads. That rollout was available to US advertisers, that is, until now.

The adCenter blog announced that the UK and Canadian ads will now be based of this quality-based ranking system. So now, for your ads to show in the "mainline" section, the ads that appear above algorithmic search results, you will need to pass a certain threshold of quality. This quality component seems to be made up of your click-through rate and maximum bid.