Twitter plans to introduce at least 15 new kinds of ads over the next six months to increase revenue and add new advertisers. A report in the Wall Street Journal said Twitter's new advertisements will encourage users to download apps.

The strategy is expected to parallel Facebook's approach to mobile advertising apps that include an "Install Now" or "Shop Now" button on their ads.

The new ad campaign will start innocuously with an ad encouraging Twitter users to download apps to their smartphones. Clicking the download link will take a user to that app's listing on the App Store.

These new ads will be an extension of Twitter Cards, which show previews of images, videos, or webpages alongside a tweet. Twitter Cards make it possible for advertisers to attach media experiences to Tweets that link to an advertiser's content. There are seven kinds of Twitter Cards.

Advertisers can add app download or purchase link to a Twitter Card. Twitter has been experimenting with other ways to use Twitter Cards to increase users' engagement with advertisers, giving users a clearer call to action in sponsored tweets.

Twitter's advertising revenue more than doubled in the fourth quarter to $219.6 million, compared with the same period last year but the company has yet to make a profit.

Twitter is now one of the 10 most visited websites, and has been described as "the SMS of the Internet." It was created in March 2006 by Jack Dorsey, Evan Williams, Biz Stone and Noah Glass.