Click-through rate (CTR) is the most common metric used to assess the performance of an online advert; another per- formance of an online advert is the user post-click experience. In this paper, we describe the method we have implemented in Yahoo Gemini1 to measure the post-click experience on Yahoo mobile news streams via an automatic analysis of ad- vert landing pages. We measure the post-click experience by means of two well-known metrics, dwell time and bounce rate. We show that these metrics can be used as proxy of an advert post-click experience, and that a negative post- click experience has a negative effect on user engagement and future ad clicks. We then put forward an approach that analyses advert landing pages, and show how these can affect dwell time and bounce rate. Finally, we develop a prediction model for advert quality based on dwell time, which was de- ployed on Yahoo mobile news stream app running on iOS. The results show that, using dwell time as a proxy of post- click experience, we can prioritise higher quality ads. We demonstrate the impact of this on users via A/B testing.