Viral marketing is quite prominent these days and refers to the marketing system where the marketer uses an individual to promote his message. This is done through emails or through the social networking sites these days. The latter is more popular and effective in the present times and word of mouth is also used for promoting the site. For instance, if you like a certain page on a social networking website, then the ad for that site is replicated and shown to everyone who is there in your friend list. Similarly sometime the advertisement is given by the mail service that you use and whenever you send mail through that then the ad is sent out to your receiver. This way you become a host and help the site to promote it. Many of the adv4rtisers use viral marketing in their campaign as it is very cost effective and can reach out to wider consumers easily. Initially hotmail used viral marketing through its email service to reach out to more people. Since then it has evolved and the advertiser uses different hosts to promote their website and get more clients. With the popularity of Social Media, the viral marketing has also developed and is quite successful.