Online advertising in the United Kingdom raked in $2.48 billion last year and is now worth three times the U.K. radio-advertising market, Ofcom’s annual report into the communications market has revealed. Now the fourth-largest display advertising medium in the U.K. behind newspapers, television and direct mail, online outstripped outdoor advertising in 2005, as well as the business and consumer magazine markets. Two big advantages of online advertising are its targeted nature, which generally suits the niche nature of the Internet, and the ability of advertisers to closely track results, which has in turn led to a variety of specialized advertising arrangements, such as cost per thousand (known as CPM in the United States) or cost per click (also known as pay per click).