That banner ad you see today on a Yahoo web page may have been triggered by a search you did on the company's search engine two days ago.
That is because Yahoo tracks users' queries on its search engine and, based on that information, tailors the graphical ads it beams at them later throughout its network of sites.
In this advertising program, called Yahoo Impulse, Yahoo captures a users’ query terms and categorises them. For example, someone who searches for the term "credit card" will be tagged as someone who is interested in the broader "financial services" category.
Then that user will be served graphical ads, such as banners, from participating advertisers in that financial services category while he is in the network of Yahoo sites.
The program is a sort of twist and extension of search-based advertising, which traditionally has involved providing a set of text ads along with the list of search results based on a user's query.
But unlike paid search programs, which target text ads to users on a one-time basis and only within the search results pages, Yahoo Impulse takes note of a user's queries to determine what kinds of graphical ads he will see elsewhere on Yahoo over a period of time.
Yahoo Impulse tracks queries through users' Yahoo cookies and serves up the subsequent graphical ads for 48 hours afterward. Yahoo Impulse has existed for about four years, but ads previously were triggered for only a one-hour period after the user's search session.
This particular incarnation of Yahoo Impulse, with the much longer 48-hour ad-tailoring period, was launched about three months ago. Advertisers sign up for the program, but it's not an opt-in program for users.