My tip for today will be "The less ads, the better" yes why do you assume that you will earn more by placing more ads ? why not putting 1 single ad unit per page and nicely fit it into the design more over, you can change it's position of colors every few days (weekly) adsense says they server the most profitable ads in the top adsense units rather than the lower units best to do is putting one single unit so you make sure the user will click an ad that pays well for you I hope this was useful one and see some reps coming already
I still think it depends on your layout and type of site you running. I tried to take some ads off last week and my earning dropped by half.
If people want to put larger units lower down the page - they can always put in referrals OR other networks banner ads (CPM) etc.
DP have always done that. The one one the top right hand side, unless the thread runs long, when you can start seeing two large rectangles. But as argothiusz says, it depends on the type of site you are running. If you have a site where the ads pay less(very low ecpms), then it is better to show many ads. But for niche sites with high paying ads, less ads sure pays. I have experienced with both.
But in the end the visitor only clicks on ad link from 1 unit no matter how many ad units on the page (putting into consideration that every ad unit has multiple links)
I use 2 add units on most sites and one on a few. I used to have 3 units on each page and took one off.
If the CPM of your website is very low, you should be show more ads. If the CTR of your website id very low, you should be show more ads and ornament your ads to assort with your website. That is my experience.
Most of the people already know this, it's basically common knowledge. Oh and I suggest you get rid of the rep begging comment since people have a tendacy to neg rep you if you do hat.
as a blogger, i put two ads in my site. one on top of the post and one after the post. im not sure if this if very effective though hehe