farmboy - 4:07 pm on Apr 26, 2010 (gmt 0)
1. Internet Explorer 4.79%
2. Firefox 3.69%
3. Safari 3.47%
4. Chrome 3.30%
5. Opera 3.20%
Maybe it's simply that after you get past #1 and maybe #2 above, the number of people using those browsers and visiting your site and seeing the AdSense ads on your site aren't enough to be statistically significant. (That's number of people not percentage of the total.)
One possible explanation is that users of alternative browsers could be considered generally more web-savvy, and they would naturally therefore be less inclined to click
...may tend to be a little more technical and maybe less apt to click on ads.
I don't follow the logic of an assumption that someone who is web-savvy or more technical is less likely to click on an AdSense ad.
I would expect that someone who is web-savvy or technical to understand that clicking on an AdSense ad is safe (relatively speaking) and a FREE way to find out about a product or service that is of interest.