Google provides a range of formatting options for its RSS ads. Some of them are fairly difficult and will need testing to get right. On the new interface, you can find AdSense for Feeds directly under the AdSense for Content link. The name of the unit is chosen for you, although you can change it later if you really want, but so is the size of the ads.

Google matches the size and the format of the ad to the format of the RSS feed. That’s a real problem. You can end up with ads that look like half-banners and you can end up with square ads that look completely different but you have no control over either. Google doles out the ads and if you happen to know that one type of ad will do better than another, tough luck. Or rather, tough tweaking, because there are a few things you can do to influence the size and formats of the ads you receive.

While you can’t choose the format of the ad, you can choose whether it appears as an image or as text. Most publishers, I think, will do better with text ads than image ads. RSS subscribers tend to be looking for the information in the content, not for pretty pictures. They want simplicity and they’re more likely to react to the links in a text ad than the picture in an image ad.

Choose to receive only image ads, and you’ll not only be drawing on a smaller inventory and therefore receiving less well-targeted ads you’ll also be restricting your ads to the image formats. Choose either to receive only text ads or a combination of text and image ads and you’ll increase the chances of receiving ads in a horizontal format that might suit your content best.

The only way to know which is best for certain though is to test and tweak. You can create channels for your AdSense for Feeds ads, so set up one channel for text-only ads and monitor the results for a week. Then switch to image and text ads, create a second channel and compare the results. The remaining choices are much simpler. Google lets you restrict the appearance of the ads by frequency and by length. You can show the ads as infrequently as one post in four, and only in posts that are longer than 500 words, if you want. The benefit here is that showing too many ads too frequently may lead to ad blindness but I think the risk is relatively small. The default position should be to show ads on all of your posts.

There may be exceptions to this rule though. When you set up your RSS feed, you can choose whether to show only a headline and a small amount of text, forcing subscribers to come to the site to read more, or to put all of the article into the feed, allowing subscribers to enjoy all your content in the reader. Before the arrival of AdSense for Feeds it made sense only to show a part of the content, and force subscribers to visit the site to read on. There was no point in giving away content for free. Now that you can place an ad on an entire article though, it is possible to give away everything through a feed and still make money.

But I wouldn’t recommend it. Those falling eCPMs suggest that you still want your subscribers to come to your site and click ads rather than use the cheaper ads in the RSS feeds. AdSense for Feeds then should be seen as a way of supplementing your regular AdSense income, not replacing it. If you have more than one feed, you could experiment by showing ads only on longer posts or on occasional posts, generating most of your income on the site and preserving a high clickthrough rate on the feeds. When the ads do appear, they might just look unusual enough to generate clicks out of curiosity.

My feeling though is that you may as well offer as many ads as possible by putting ads at the bottom of article introductions in feeds. That should increase your chance of winning clicks. You can’t choose the format, but you can choose the position of the ad unit: you can put the ads at the top or you can put the ads at the bottom. That’s not much of a choice. What you really want to do is embed the ads in the middle of the article and force readers to look around them. But you can’t do that, so of the two options available, the best one is usually to put the ads at the top.

That’s surprising. The bottom of the post feels more natural and it’s the option taken by many publishers. You can even end a post with a list of links and blend the ad neatly into the post. That’s easier to do at the bottom of an article than at the top.

But not everyone reaches the bottom of the post and the advantage of appearing above the fold outweighs any benefits that blending might bring at the bottom. When blogging expert John Chow moved his AdSense for Feeds to the top of the post, he found his clickthrough rate doubled. It really was as simple as that. Finally, you can let AdSense choose your color scheme for you or you can do it yourself.

Do it yourself. Lose the border, of course, and match the color scheme to the colors used on your feed. You won’t be able to see how it all turns out just by refreshing the page but you should still check to make sure that it all turns out exactly as you want.

AdSense for Feeds is a relatively new product and it’s one with an uncertain future. The use of RSS readers is falling and that drop in popularity is being reflected in the falling value that advertisers are placing on ads that appear in feeds.

But they haven’t faded away yet, and they’re unlikely to fade away completely. Social media might be a good way to receive content recommendations from friends and even to receive automated link updates from favorite blogs but they’re not as organized as RSS readers. While their use may decline, it is still worthwhile for an AdSense publisher to push out headlines and small amounts of text to subscribers as a way of bringing them back to the site. And despite the falling eCPMs, it’s also worth including an AdSense unit in those feeds.