So, you've set up your ad campaign for Bing in adCenter and now you want to know whether or not the ads are showing. Now, you can with a new feature called Ad Preview.
The adCenter team has added this feature due to much request from advertisers. The Ad Preview enables advertisers to check their ads without artificially padding the impression and click data.
If you find your ads showing in Ad Preview but not in a regular search, remember that you might have set demographic and/or geographic targets that you yourself do not meet. Also, you may be outbid at the time you check an ad on the regular search. Ad Preview, however, does not currently provide a geographic or demographic preview, but they're working on it and hope to release it soon.