We're excited to announce that the new ranking model is now live in our UK market. The new ranking model is designed to improve user results through higher quality search ads. When users engage with these higher quality search ads, advertisers will receive more interested, valuable potential customers, helping to drive better results for your business.

As we previously announced, both bid amount and ad quality
now determine an ad's rank in search results.

Your bid is the maximum amount that you're willing to pay when your ad is clicked. You will never be charged more than this amount.

Your ad's quality is determined by:

The ad's historical performance-determined by its click-through rate relative to its position on the page.*
The ad's expected performance, relative to competing ads displayed at the same time-determined by various relevance factors considered by Yahoo! Search Marketing's ranking algorithms.

- Yahoo!