Google uses its technology to serve advertisements based on website content, the user's geographical location, and other factors. Those wanting to advertise with Google's targeted advertisement system may enroll through Google Ads. AdSense has become one of the most popular programs specializing in creating and placing banner and responsive ads on website and blogs. Responsive ads adjust themselves based upon user's device size. These advertisements are less intrusive and the content of the advertisements is often relevant to the website. Many websites use AdSense to make revenue from their web content (website, online videos, online audio content, etc.), and it is the most popular advertising network.[6] AdSense has proved particularly useful for generating advertising revenue for small websites that do not have sufficient resources or other major sources of revenue. To display contextually relevant advertisements on a website, webmasters place a brief Javascript code on the website's pages. Websites that are content-rich have been very successful with this advertising program, as noted in a number of publisher case studies on the AdSense website. Google has removed the policy of limiting AdSense ads to three ads per page. Now, Adsense publishers can place several AdSense ads on a page given there is sufficient content on a webpage. According to Google guidelines on ensuring proper ad placement, advertising and promotional material should not exceed page content.