Can't See Your AdCenter Ad on MSN Results?

During the AdCenter pilot some users have expressed frustration with not being able to see their ad on MSN search results pages. The primary cause for this is that AdCenter ads are only being served 25% of the time right now.

I have seen a few of my ads on MSN but those instances have been few and far between. I found out today that the ads (AdCenter or Yahoo based) people are served on MSN are the result of a cookie on the users machine. I must have deleted my cookies and have a cookie that causes me to see the Yahoo based ads now.

Anyway, ads shown in the results of searches from here are all AdCenter driven ads:

adcenter.search.msn.com

If your an AdCenter user and like to see your ads in action from time to time that's the place to do it.