In a simple manner, Web advertising can be defined as an advertising that uses the online Web site as an ad vehicle. Especially, the Web advertising shows many of differences from the advertising on traditional vehicle, such as TV, Newspaper and so on. The Web advertising not only has no time and distance limit, but also makes well segmenting the target audiences and uses various multimedia functions. In addition, advertisers can measure the effectiveness of the Web advertising in real time. It makes many advertising practitioners well control the advertising effectiveness and audience responses. There are also many different types of Web advertising (Schumann and Thorson, 1999):
Banner advertising: Banners can be purchased throughout the Web and provide direct links to homepages. They account for 54 percent of online advertising revenues.
Sponsorship: Promotes certain forms of online content such as contests and give-aways. Also, sponsorship is somewhat analogous to event marketing.
Content web sites: Business web sites promoting the company and its products/services.
Classified advertising: Web site providing targeted promotion of products for sales.
Directory listings: Listing of companies can be found on certain homepages or search engines.
Inline Ads: Online advertorials positioned within a web site.
Interstitials: Flashes of branding information or imagery often appear between pages and site.
Pop-up windows: Separate windows that appear on top of site content while a page is loading.
Split-screen ads: A web site screen is split between advertising and content.
Among them, banners have proven to be the most effective advertising tool, producing quantifiable units to which an advertiser can apply readable metrics and make real conclusions with real numbers about the effectiveness of the campaign. Also, banner advertisements can appear in numerous forms. Many sites offer numerous forms of advertisements such as buttons or vertical opportunities. Likewise, ad banners remain the predominant advertising vehicles on the Web-accounting for approximately 54% of total Web advertising revenues (www.iab.net). Moreover, for banner ads, the traditional involuntary exposure concept can be applied because Internet users can be only exposed to the banner ads without clicking them to open to see linked target ads. (Cho, 1999)