are static, while others change; for example, continuously or periodically rotating among a set of advertisements. Mobile displays are used for various situations in metropolitan areas throughout the world, including: target advertising, one-day and long-term campaigns, conventions, sporting events, store openings and similar promotional events, and big advertisements from smaller companies. Point-of-sale In-store advertising is any advertisement placed in a retail store. It includes placement of a product in visible locations in a store, such as at eye level, at the ends of aisles and near checkout counters (a.k.a. POP – point of purchase display), eye-catching displays promoting a specific product, and advertisements in such places as shopping carts and in-store video displays. Novelties Advertising printed on small tangible items such as coffee mugs, T-shirts, pens, bags, and such is known as novelty advertising. Some printers specialize in printing novelty items, which can then be distributed directly by the advertiser, or items may be distributed as part of a cross-promotion, such as ads on fast food containers. Celebrity endorsements Advertising in which a celebrity endorses a product or brand leverages celebrity power, fame, money, popularity to gain recognition for their products or to promote specific stores' or products. Advertisers often advertise their products, for example, when celebrities share their favorite products or wear clothes by specific brands or designers. Celebrities are often involved in advertising campaigns such as television or print adverts to advertise specific or general products. The use of celebrities to endorse a brand can have its downsides, however; one mistake by a celebrity can be detrimental to the public relations of a brand. For example, following his performance of eight gold medals at the 2008 Olympic Games in Beijing, China, swimmer Michael Phelps' contract with Kellogg's was terminated, as Kellogg's did not want to associate with him after he was photographed smoking marijuana. Celebrities such as Britney Spears have advertised for multiple products including Pepsi, Candies from Kohl's, Twister, NASCAR, and Toyota. Aerial Using aircraft, balloons or airships to create or display advertising media. Skywriting is a notable example. New media approaches A new advertising approach is known as advanced advertising, which is data-driven advertising, using large quantities of data, precise measuring tools and precise targeting. Advanced advertising also makes it easier for companies which sell ad-space to attribute customer purchases to the ads they display or broadcast. Increasingly, other media are overtaking many of the "traditional"