If positioned well, ad formats can increase your earnings significantly. In my site, the formats I found to be the most effective are the 336x280 Large Rectangle, the 300x250 Medium Rectangle. The format that best complements my pages are 300x250 Medium Rectangle on the home and single pages. (integrated on the content). and a 300x250 Medium Rectangle on the left sidebar. And you? Which ad format You use?
I use 336x280 and 300x250 for my blogs and 728 x 90 for entertainment sites like arcade and video niches.
Any size can be a good choice but it's totally depend on your site's template design or layout. Most of the time I used 300x250. .SR
And we have a winner The format of the ad depends upon the format and layout of the page that it is placed on. I use a variety of ads on my pages since they are formatted differently. I usually only have one ad on a page but will often throw the link units at the bottom as they are good performers for me.
336x280 ad formate is better and i use this formate with adsense integrator plugin and this combination works better.