Most of us are using the most famous "easy adsense" plugin. Easy adsense by Manoj Thulasidas Even I'm using it for my all blogs. In the recent update (v 2.57), the author has decided to show "HIS" advertisements on your blogs instead of your adsense unit for at least 1% instances/pageviews. The default value is set to 5%. Now I do not need to tell you that if you do not pay attaintion, your 5% of profit will go into his pocket. I immediately removed the plugin, and inserted the ads manually. You have following options: 1. Remove the unit and put ad code manually. (Not very flexible, if someday you choose not to show mid-post ads and want to show all of them at post bottom, you will have to edit all posts) 2. Let him take your at least 1% profit (the plugin it amazing and you should be enough big hearted) 3. Search for other plugin. (I'm doing this, if you find any better, let me know too.) But again you do not have guarantee that it will "ALWAYS" show your ads only.