Hi. I would say its Text Ads. With articles being text, if you can get your ads to blend in, they will have more chance of people clicking them. I'm guessing you were asking which ad format, but if you meant what your ads should actually be, then thats hard to say as i am not sure what articles you are talking about.
I have a web-blog sprinkled with banner ads. However I need to optimize it since it's not converting well. We need an optimizing thread
You will never know what converts for your content without testing. I'd suggest your try three different things as a good starting point: 1. Adsense - Let Google take care of attempting to match ads to your content. 2. InfoLinks - Some people have great luck with InfoLinks.. 3. Affiliate Offers - Either link appropriate text phrases to the offers, or insert an appropriate banner at the right location. I prefer to put a banner within my article/post and not just at the top of the page. 3% CTR using what? How targeted are the ads to the content? What types of ads/offers?
You might want to try adsense, i've always had good times with those. I typically use the 350x300 size, i believe that's the right size. I kind of forgot. But CTR is alot more than just the network your with. You also need to have great + relevant content, and place them at high-ctr hot spots.
Some type of webpages aren't proper to adsens for example you earned 10$ by CPM Networks But con't succeed in ppc Networks
I would say default ads which Adsense offer, image/text.. You should position them in before heading, after post and one 160x600 in sidebar...