Philipp Lenssen has received a tip from Gal of 60in3.com about Google AdSense, here is what Gal has to say —”I use Google AdSense on this site but I kept on seeing issues with some ad units showing up as blank. Turns out Google tries to fill in the ad units from top to bottom. If they don’t have content for ANY of the ad units, they stop. That means that if just one of your ad units doesn’t have content from Google, none of your later units will either, even if they’re simple text ads.
In my case, I have an image ad block at the top. Since image ads are rarer than text ads, Google would often have a problem filling this ad block and would substitute in a PSA [public service ad]. This would cause AdSense to not try and fill in any of my other ad blocks even though they were simple text and link ads for which Google has plenty of content.”
Lesson learned, don’t put ad blocks with images at the top or don’t use them at all. Including the text Google sent me here:
Because you’ve chosen to display ’image ads only’ in the first ad unit on your page, it’s likely that you’ll see PSAs. Image ads are still new to advertisers as well as to publishers, so the available inventory of image ads for your content may be low. Please note that the first ad unit on the page is the first to be ’filled’ with ads, so if no ads are available for the first ad unit, your other units will not display ads.
I understand that you may sometimes see ads appear in the first ad unit after refreshing the page. At this time, AdSense uses technology that determines a web page’s meaning and serves ads from our pool of AdWords advertisers that are relevant to that page at that moment. In addition, the available advertisements depend on the budget and criteria an advertiser has selected for a specific campaign. As a result, you may not always see ads available for your ’image ads only’ unit.
I’d recommend updating your ad code to display both text and image ads, to take full advantage of our ad inventory. To do so, you’ll need to regenerate your ad code from within your account.
However, if you’d still like to show only image ads in your first ad unit, you may wish to implement an alternate ad by following the instructions at http://www.google.com/adsense/alternateads
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