yesterday i got message from adsense in my account asking me to remove 468x60 banner ads and replace with 728x90 as they perform more better. Looks like 468x60 size is losing popularity among advertisers and visitors too most blogs and sites have content pages with width almost 600px, so i wish adsense adds 600x60 or 600x90 sizes instead of 728x90
I wish i can get this email as well... yeah but i dont use 468x60 banner.. There is no harm in following google adsenes advise.
i removed 468 x 60 ads from top of each page/post and instead added a 300 x 250 square box on left of content in each page/post. My impressions/day remained almost same but clicks increased by 70% and income doubled from that day
They are just telling you the 728 banners do better. In most cases anyway. For me the 728's have worked better since they change them to one line ads instead of 3 side by side. still you may do better with the 468, experiment. Somebody posted above good earnings from a 468. Some niches do better with them like using them as image ads on game and music related sites were there easy to fit into a tight space and blend into the site nice and fit right. Try them both-on all your sites.
What works for one site may not for another. Depends on the site, layout, and design. All you can do is experiment and test different sizes, formats, and different locations on your site.