I see frequent posts on webmasterworld.com: 'My AdSense revenue/EPC/eCPM is/are down, what's going on?' - the conversation often degrades into a slam session asserting that it's all a conspiracy or the phases of the moon may be factor - so, I've been thinking of some of the things that a webmaster can control, and those that can't be controlled.
Here are things I have discovered over the years: It is important to focus on the things that you can control, and not worry too much about the things you can't control directly. I find it more productive to focus on the things that I can change, rather than dwell on something totally out of my reach, such as Google's motives or need to increase this quarter's profits.
Things you can control
Here are some of the things that you can try to control, in order to improve your site's performance.
Where are your ads being displayed? Some debate the usefulness of the heat map but you have to start somewhere - optimization of ad placement and layout is critical to getting visitors to notice ads in the first place - if they don't notice them, they surely will not act on the ad's content. This is critical to avoiding ad blindness.
What ad formats are you using? Have you tried optimizing the ad formats being used? I find that certain ad formats result in dramatically higher eCPM and click-through rates. This is critical to avoiding ad blindness.
Ad colors and blending
Blending may also play a key role in avoiding ad blindness - but beware, you can incur the wrath of Google, and piss off your site visitors, if you overdo this.
Also consider using color palette rotation.
Link units? Text ads? Image / Flash ads? Referral (CPA) ads? Choosing the optimal blend of ads for your site's visitors may be crucial to your success.
Number of ad units on a page
How much 'inventory' are you offering? Are there enough advertisers and ads to fill all available ad placements? Greater inventory relative to keyword demand can lead to lower priced or off-topic ads showing on your site. Sometimes, less is more!
Site content and quality
Does your site content mesh well with incoming visitors, and are those visitors likely to appreciate the ads on your site?
Are you writing for the web?
Site content keywords
Google uses these to determine which ads to display, and therefore basic EPC will flow indirectly from the site content.
Site URL structure
Google uses these to determine ads to show while waiting to spider your new page!
Site navigational elements
Is your site's navigation well thought out? Can visitors find what they are looking for? Is your site a pleasure to use? These factors all have an impact on visitor loyalty and time spent on the site.
Visitor loyalty and time on site
The number of repeat visitors and the amount of time spent on your site by each visitor are crucial indicators of visitor satisfaction with your site. If you check your logs and find that people rarely visit more than one page before leaving, or spend little time on your site, then you might want to consider whether your site's content or structure needs improvement.
Why are visitors leaving your site? Why do they stay? Do you know?
Try to increase traffic
This is something that may be within your control - but then again, maybe not (see below.) You can gain new/increased traffic but it's often indirectly related to your efforts - it's still something that you can work on, and usually has a positive effect.)
AdSense section targeting
Help Google improve ad relevance by telling the 'bot about the structure of your page - what's relevant to the page content, as opposed to navigation or other non-essential content?
Things you can't control directly
Actual site traffic at any given moment
What if overall web surfing is up or down 20% today over yesterday due to some external influence? What about seasonal factors? If it's springtime or summer vacation time, people are out living their lives, not surfing the web.
Advertiser budgets and spending vary on any given day or at any hour. What happens when a few of the major advertisers whose ads appear regularly on your site hit their daily spend limit due to clicks that happened on another site? Your ad revenue will drop!
Has the Big G decided your site should be discounted? You can try to control this, but ultimately, it's all up to Google.
This affects visitor click-through probability - will any particular visitor click on an ad? Is the ad relevant to that visitor? Will the ad shown to a particular visitor be the best ad for that user, increasing the likelihood of a click? The ad rotation may have a negative or positive effect depending on timing, site visitor patterns, etc. Google supposedly tries to target AdSense ads to the visitor based on search terms, browsing history, etc. but this is still a gray area.
Earlier, I hinted that you can try to avoid this with ad placement and format, or blending. But ultimately, if a majority of your site visitors are blind to ads in general, you aren't going to see much action unless you play some underhanded games.