Control the order of ads?

Can I control which ad block gets the "top" ads?

[martingale]

I have two ad blocks on my site: Left column, and center block. The center block ad visually appears at the top of the page, and the left block visually appears half way down the page. However, in HTML the left column comes before the entire center block.

Obviously the center block ads are going to get more clicks, but I've noticed that AdSense seems to run the top ranked ads in the left column (first in HTML) rather than at the top of my page. Is there any way to tell AdSense which ad block is "first" so that I can ensure the top ranked ads are placed in the most desirable location?

I could rework the page so that the top block is actually first in the HTML too, but then things wouldn't look as nice as now, so I'd rather not.

[Jenstar]

No, the only way AdSense does it is by giving it priority based upon what ad unit appears first in the html.

[linear]

With CSS posiotioning, the first in code block need not be the first on page block.

So same answer as Jenstar, but change "No" to "Yes" :D