I got a very interesting question in my inbox today. The question is – AdSense offers two rectangle ad units – 300×250 and 336×280. Which one is better? Also many people recommend 336×280 but I see most of them use 300×250 and I see the same on your forums/blogs.
It is a very tricky question where he is not only asking me why I am using an ad unit that is not best recommended by others.
I will answer this question in two parts but before we begin let us see the Adsense Rectangles first.
Adsense does not offer two rectangle ad units but actually they offer three rectangular ad units.

336x280

300x250

180x150
Coming back to the original question -
Which Adsense Rectangle Ad Unit performs better?
As a general feeling we may think that the larger the ad space the better it’s earnings will be and this is the main reason why some people suggests 336×280 over 300×250 but 300×250 is much more popular among advertiser’s and especially among the CPM ad networks. In Adsense you can opt for Google certified CPM Ad network ads and so if you have 300×250 it may actually have more advertiser’s to compete for an ad view giving you higher return. So instead of going with what I say is best, test both as there’s a good reason why the smaller ad unit can perform better for you and vice versa.
The other part of your question is -
Why I use 300×250 more than 336×280?
Adsense is not the only Ad network I use. The other network prefers 300×250. It is one of the main reason I prefer 300×250 ad units more than 336×280. Apart from that I personally like 300×250 integrated into the design more than 336×280 because later looks less professional to me.
How about sharing your best performing Adsense rectangle?
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im applying side by side ads using tables. one text and the other one just image.
Great and how is it performing?
. my site is new although my domain is old. not getting enough traffic yet
I would recommend not to have Ads on your site then because that would mean you can concentrate on building your site and not worry about few cents here and there.
How is AdSense for Search going for you? For some reason my users are not clicking on the ads. I’m starting to think because of the “search entire web” option.
The search is an option for users and if I make something I am fine with it but the search is not where I prefer to make money.
There are several things to consider about performance. And I’ll give brief example.
1. Are your ads matching up to the reason your traffic visits. For example: I have several sites that use the EXACT SAME TEMPLATE and colors and Ad Placement. One site pulls less than 1% and another over 5%. So why the difference? One reason is the site pulling the high click through is PRODUCT based. People are looking for information on a specific product. Where the other site is information based, they want to know/learn about what is available in the market segment. Product sites in my experience always win out with Adsense.
2. Are you using Text only, Mix, or Image only. I’ve tested this to death and over all Text Only always performs better. However there are times when Image Ads will pay a lot higher on a per click basis.
3. Placement. Above the fold and in content is a winner. Side bars are not. Properly placed text ads at the end of quality content that you visitor actually reads and relates directly to the content will perform well. So there is no reason to put ads all over the place to “fill space”. If you want to get clicks integrate into your content.
4. Colors. Yes it seems to work best to integrate with the colors of your site, having said that all things equal I find that blue text links on white backgrounds will out perform everything else.
So what is better 180, 250, 300, or 336? While there is no definitive answer due to variables, the 300 block seems to be the best choice over all in my experience. Advertising networks like this size and will take the time to produce creative for this size. 250 is not very common in most ad networks.
There you have it. Nothing resolved
I think it matters depending on your website layout and width.
Shabir, is it allowed to place adsense ads in the middle of a single post? I have seen many site which is having ads in the middle.
If allowed, how to do that? I did not find the way in blogger or adsense.
Yes it is allowed but you should have the plugin to get that done. In Wordpress I know how but am not an expert in blogger interface but I am sure there is a way to get this done.
I simply copied my adsense code inside HTML tag inside each blogger post contents. I think this is the only it can be done with blogger.
I hope that is permitted with adsense. Ads are displaying.
I think after Google switched the URL of leaderboard from columns to row based I see leaderboard outperforms for me.
This is exactly what I wanted to say. I think the performance of leaderboard is increasing all the time with the new way of link placements.
This is really exciting stuff. Experimentation can take you long way when it comes to being successful online.
I also read that best placement is rectangular ads but now I know which rectangle performs better.
I also read somewhere that 2 rectangles placed side by side works the best and will you comment on such ad placement.
Yes they do work well enough and I have such placement on some of my sites and especially forums.