About Google Adwords
And motivated by a thread at the Warrior Forum;
What is placement-targeting?
“Placement targeting (formerly called site targeting) lets AdWords advertisers choose individual spots in the Google content network where they’d like their ads to appear. A placement might be an entire website or a subset of a site, such as only the sports pages of a news site. You handpick your audience, big or small. The AdWords matching system does the rest, analyzing your input and creating a list of available content network sites for you to choose from.
Anyone who has an AdWords Standard Edition account can run placement-targeted …read more

Offer valid until 12/31/2007, from Google Adwords;
“Very often, your customers and prospective customers begin their search for a service or product on Google. When you target prospective customers searching for just what you offer, you can get your business growing. Try Google AdWords for free and get $50 worth of free marketing for your business – no strings attached!”
More…
If you can describe your business in 2 lines, you can take advantage of this special marketing offer (worth $50) for your business.
To claim your special offer advertising with Google AdWords:
1. Set up your account and create your campaign (it’s easy).
2. Open …read more

From this post at Inside Adwords – Ten possible reasons you can’t see your ad on Adwords;

Your ad has been disapproved.
The keyword you used to search for your ad is not performing well and has become inactive for search.
Your ad rank is not high enough to allow your ad to show on the first page of search results.
Your ad is showing, but in a lower position possibly due to a shift in the competitive landscape.
Your regionally targeted ad doesn’t include the region (e.g. city, state, or country) associated with your computer’s Internet Protocol (IP) address.
Your ad is targeting a language …read more