I am using adsense responsive format which is great for mobile users as almost 80% of my users are coming from twitter via mobile device. But I have one problem that somehow I can't solve it. When opening an article via PC the responsive ad is with a 468x60 format and I don't like it at all. I would like the format to be 336x 280. The only way I can do this ( I thing its the only way ) is to add a html box inside the article(wordpress) that has this dimensions and the ad will fill. The problem is I don't know how to do this, if anyone can help me with this or guide me to an article to my solution.