Should I use the 300x250 Adsense Rectangle or the much wider 336x280 for maximizing clicks? What do I select - 4 or 5 ads per adlink unit ? Will text only ads perform better than text+image ads ? Should I hide the colored border ?

These are some very common questions among web publishers especially those who have just gained admission to the University of Adsense. While the answer is to keep on experimenting, most Adsense experts employ a simple technique called "AB Split Testing" to optimize their Adsense ads.

The basic idea is to display different Adsense formats at the same location simultaneously but randomly. [This is done using the random() function in Javascript that generates a number between 0 and 1 with equal probability]

Here's a sample scenario to help you determine what format works best for your site - 300x250 or 338x280 ?

Step 1: Create two custom Adsense channels - name them as 300x250 and 336x280.

Step 2: Generate the Adsense Javascript code for each of these Adsense formats. Everything will be common in two code snippets except the value of following variables: google_ad_channel, google_ad_width, google_ad_height and google_ad_format.

Step 3: This is an important step, you will merge the two Adsense snippets in such a fashion that each makes an appearance on your web pages nearly 50% of the time. Here's a sample code:

<script type="text/javascript">
 var google_ads = Math.random();
    if (google_ads < .5){
      google_ad_channel = "300x250Channel";google_ad_width = 300;
      google_ad_height = 250;google_ad_format = "300x250_as";
    } else {
      google_ad_channel = "336x280Channel";google_ad_width = 336;
      google_ad_height = 280;google_ad_format = "336x280_as";
    }
      google_ad_client = "pub-xxx";google_ad_type = "text_image";
      google_color_border = "FFFFFF";google_color_bg = "FFFFFF";
      google_color_link = "0000FF";google_color_text = "000000";
      google_color_url = "0000FF"; 
</script>
<script type="text/javascript" 
      src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>

Monitor the performance (CTR, eCPM) of the two Adsense channels for a week or two to know which of the two Ad formats are converting better. [Switch to Advanced reports, select the two Adsense for Content channels and group by both date and channel]

In the next iteration, you may try the same trick with two different color schemes but keeping the Ad format same - just create separate Adsense channels for each color scheme.

If you are displaying Adsense ads on the homepage of blogs or other places where content changes very frequently, it's a good idea to test between Text and Text+Image ads.

The contextual ads may not be very relevant on blog homepage or archives because of the dynamic content and therefore CPM based Image ads may bring in more revenue.

Related Reading: Google Adsense Tips and Tricks