Join Web Advertising Companies

What are Web Advertising Companies?They are Providing us advertisements of different companies and websites.They acts as the media between advertiser and publisher.They get money from the advertiser for giving advertisements in the websites who joined them for ad placing.Then after joining that Advertising Company they are Providing us ads from them and we are getting paid by the Web Advertising Companies.They take commission for standing as a media between advertiser and publisher.Usually not all Web Advertising Companies are allowing Blogs to their Publisher.They are looking for the registered domain websites such as www.somesite.com.But now a days Some Web Advertisements Companies are allowing blogs to be registered under them as publisher because they got the point the blogs readers are high now and as they only want visitors to attract the advertisements.