I have room in the header of my website for ads. I've tried 480x60 banner ads and text ads from several networks, relevant to the subject matter of the website and every type of ad has performed very poorly. Skyscraper ads in the left nav perform much better. Are there best practices or research that deals with the best type of ad to place in the header of a website? Or, is there a common ratio that relates performance of banner ads vs. skyscraper ads?
For reference, clickthrough rates on targeted email campaigns can often see success rates in the low single digits. Pull up your traffic (absolute uniques) subtract yourself and your clients from the mix, then multiply by .05. That should give you a pretty good sampling of how low the success rate can be. If you are using Google Adwords as your delivery mechanism, you can also track via their control panel.
Google makes so darned much money because:
a) they have insane traffic hitting their sites b) they deliver on a mind-bending array of media and categories c) they broker the deals as opposed to just waiting for a viewer to click on their sites d) they tailor the ad specifically to what the user is looking at
Generalizing heavily here, UI studies say things placed high on the page are generally going to score well in the measure of the user's attention. That's not to say that other positions wouldn't work better...that's your challenge as the designer to figure out. A visually attractive ad (and site) will help. As will quality content on your own site that invites the user to linger and be exposed to the ads.
Personally, if I'm placing an ad with a focus on max revenue, I'm going to make it stand apart from other elements so as not to lose it in the flow. I find when I'm browsing if I see a tight grouping of ads, I immediately get away. The only exception would be text ads which I might consider "hiding" among real text content to "sneak" some unintended extra clicks. I feel a little conflicted about trying to trick my user, however.
It's a tough business trying to make it solely on pay-per-click these days. Good luck.