What is contextual advertising?

Contextual advertising is widely implemented by search engines. The service offers to place ads on pages that are geared to the audience likely to visit the site. The roots of online contextual advertising were first based on personal profiling, which exploded in 1995 with the advent of permanent cookie technology. However, contextual advertising based on surreptitiously profiling the surfing habits of individuals was considered invasive and, according to countless polls over the years, highly objectionable by the majority of the surfing public; most internet users do not want to be profiled in order to be served contextual advertising.