1. Less is More I believe the theory behind this lies within thevisitor's experience at a website. If you serve up let's say...a 728x90 leaderboard, and a 160x60 side block, and maybe even anextra ad unit or link unit then you aren't just showing thetop-paying ads, you're also showing a lot of the ads with lowervalues too. This is especially painful if your site onlytriggers ads in the $2 range. These low-paying keywords can be adistraction to the visitor and while the recommended "slop ofgravy on top with a side of mashed potatoes" (describing sitesusing the 728x90 and 160x60 ad blocks on a page) has often beentouted as the best placement for Adsense, it is being proven bymany to not be all that tasty. Why? Because these ads are"outside" of your content, not within it. When Adsense ads areplaced within the body of content, it generally performs betterfor many. I have seen this myself in testing different Adsenseplacement methods. One site I own jumped in CTR by 10% when Iremoved the full meal deal and opted for a small 468x60 text adblock within the body of my content.

2. Keyword Density While Google doesn't reveal the specifics onthe methods behind their Adsense madness, most people havelearned through experimentation that keyword density plays asignificant role. Adsense does rely on the content to determinewhich ads to show, and they want their ads to be shown. It wouldalso appear that content towards the top of your page has agreater influence over the ads. It's almost a passive way offorcing Adsense users to boost their keyword density to not onlyshow the most relevant ads, but to improve search enginepositioning which improves the chances of those ads being seen.Perhaps an underhanded means of thumbing their nose to MSN,which seems to feed on keyword loaded sites these dayspropelling many an Adsense website into it's top rankings.Either that, or I've been watching too many shows aboutconspiracy theories.

3. Less is More - or More is More? Another theory is that usingfewer internal links on your webpage gives visitors fewer"click-away" options, thus improving chances of them clicking onAdsense ads. If you have 20 links on your page and let's say 4of them being within a 728x90 ad block, then visitors still have16 other links to choose from beside the meager 4 Adsense links.Keep only 5 links on the page, and they now have only 9 links tochoose from other than Adsense ads. Add more Adsense ads, suchas a block containing 5 more links carefully weaved into yourcontent (such as a 336x280), and they now have a better chanceof getting clicked on with a ratio of 9:9. Taking it a stepfurther, you could also factor other numbers into the equationsuch as : percentage of page scanned before clicking away,percentage of page scanned before scrolling, number of averagescrolls per page to predict good places to place ads, etc. Theodds can definitely be in your favour with this tactic. Ihaven't aggressively tested this theory yet and with a blog thisis certainly not an option, but I have noticed on another site Iown this might explain the 20-40% CTR I'm seeing on pages whereall internal links are at the bottom of the page.

4. Using Images Next To Ads While it's reported that Adsensedoesn't like images placed next to ads which appear to be servedby Google, this has been proven by many to boost CTR incredibly.And because these images are different than those which causedthe worldwide pandemic of "banner blindness", people are morelikely to notice them. It really just makes sense. Human beingsare visual creatures. From the time we were monkeys popping ourheads over the grass to see if a lion was coming our way, oureyes have always been our first tool in evaluating a situation,and of course, checking out other monkeys. But back toAdsense..... even more effective is when you use images thatillustrate the content of the page. I've used this trick andfind it reallly works well.

5. Font Type and Size This was announced on the official AdsenseBlog recently and it's a great tip. Adjust your page's font andsize to match Adsense ads can greatly boost CTR. This could bedifficult if your site has a lot of static pages, but a simplebatch search & replace tool can help you speed things up. Nowfiguring out what the matching font is has been a chore formany. I believe (through trial and error) that the font usedmainly in Adsense ads is Arial, size: 11px A number of peoplehave reported that they've witnessed Adsense ads conforming totheir page's CSS font styles. If anything is occurring here, I'mwilling to take a guess that Adsense ads might be able to adaptto a very limited number of fonts and if you happen to use oneof those fonts on the page, it will change accordingly. But as Isaid, if this is true than I think it's limited. After all, haveyou ever seen an Adsense ad in FontLeroyBrown 20px ?

6. Test, test, test Nearly everyone agrees that Adsense is onlyas effective as the unique way you integrate it into yourwebsite. What works for one person may not work for another.While there are some basic principles which are great startingpoints for any website, your design and content is unique andtherefore visitor behaviour will be unique. Your best resultswill come through experimentation and patience.