From SEW Forums:
We have a new option within Adwords. See below. Ultimately, you can try and determine the position of specific keywords within an account. If you go into Edit Settings you can activate this for each or all the campaigns and then decide at KW level.
Position preference lets you tell Google where you would prefer your ad to show among all the AdWords ads on a given page.
Whenever you run a keyword-targeted ad, your ad is assigned a position (or rank) based on your cost-per-click (CPC) bid, your keyword’s Quality Score, and other relevant factors. There may be dozens of positions available for a given keyword, spread over several pages of search results.
If you find that your ad gets the best results when it is ranked (for
example) third or fourth among all AdWords ads, you can set a position preference for those spots. AdWords will then try to show your ad whenever it is ranked third or fourth, and avoid showing it when it is ranked higher or lower. If your ad is ranked higher than third for a given keyword, the system will automatically try to lower your bid to place your ad in your preferred position.
You can request that your ad be shown only when it is:
* Higher than a given position (such as above 7)
* Lower than a given position (such as below 4)
* Within a range of positions (such as from 2-8).
* In a single exact position (such as position 2).
You can choose any positions between 1 and 10+ (that is, 10 or any larger number). Separate position preferences can be set for any or all of the keywords in your campaign.
Please note that position preference does not mean that your ad will always appear in the position you specify. The usual AdWords ranking and relevance rules apply. If your ad doesn’t qualify for position #1, setting a position preference of 1 will not move it there. Position preference simply means AdWords will try to show your ad whenever it is ranked in your preferred position, and to avoid showing it when it is not.
Position preference also does not affect the overall placement of AdWords ad units on the left, right, top or bottom of a given page. It only affects your ranking relative to other ads across those units.
Position preferences are not guaranteed. Your ad may still appear in other positions, though we will make every effort to display your ad where you prefer. Once you set new position preferences, it may take a few days for the AdWords system to begin delivering your ad according to those preferences.
Finally, let us note that setting a position preference can sharply reduce the number of impressions and clicks you receive for that keyword. Targeting just one or two positions means your ad will not show at times when it otherwise might have. We encourage you to choose as broad a range of positions are you are comfortable with.