Google Showing Single Large Text Ad Instead of 3 Regular Ads

[PaulPA]

I have 3 ad Adsense text box set up throughout my site. However, I've just started noticing that on some pages a single ad in large text is taking over the entire box. I assume that this means that only one ad is filling that area of my site but is there a way to control it so that it remains as a single regular sized text ad?

[PaulPA]

Actually with a little research I now see this appears to be Google promoting their own service in the form of Urchin. Anyone else seeing this? Single Urchin ad instead of multiple text ads?

[hunderdown]

That's probably a CPM ad. Read up on that in the AdSense Help area.

[PaulPA]

Right - I know about CPM ads but I thought there was an option not to allow these to show if an AdSense account wanted to stick with the regular text ad layout. But I can't seem to locate that option.