Unless you fell upon this story by chance, it's likely you found it using a search engine provided by Yahoo! (nasdaq: YHOO - news - people ) or Eric E. Schmidt's Google, entering keywords such as "search engines," "advertising revenue" and "Internet."

Most search engines do their text query and retrieval using keywords, which tell a user something about the subject and content of this page, then navigate him there. And unless the author of the Web document has specified the keywords for his or her document--by using so-called meta tags--the search engine will determine them by indexing words that appear to be significant.

Read more about the U.S. Internet advertising revenue and Google Adwords' role at http://www.forbes.com/work/management/2005/09/27/google-ad-revenue-cx_cn_0927autofacescan01.html.