Give more advertisers access to XXXXXXXXXX.com Opt in to Text and Image/Rich Media Ads We found that 271 of your ads aren’t enabled to help you achieve your maximum earning potential. Currently, 66% of your units are only opted into text ads and 1% are only opted into image/rich media ads on XXXXXXXXXXX.com. We recommend that you opt in to both text and image/rich media ads for all your AdSense ad units. Upgrade your units! Select all ad units From the Actions drop-down, edit ad type to "Text & Image / rich media ads" On average, publishers see a 80% increase in eCPM earnings when they make these recommended changes. Enabling your units to display both text and image/rich media ad types increases the number of ads competing to appear on your site. More advertisers in the ad auction drives higher bids and more revenue for you.
I followed their tips as soon as I got it. I believe my earnings will shoot up. Thanks for your concern.
I guess Google is sending tips to users so that the advertisee's will also get more clicks, therefore making Google more money.
I've had google tell me to put 3 ad units on my sites because most of them only have one, they just send optimisation tips every now and again.