1. Introduction
With the help of different information and communication technologies, the time that people spent on the internet increases. Customers also increasingly prefer to use online sites to buy goods and services and internet becomes the main sales and marketing channel for many industries. Among them, travel industry is one of the first and successful industries to use internet for doing the business. According to PhoCusWright, travelers will book one third of the world's travel sales online by the end of 2012 and online travel bookings will grow twice as fast as the total market. In addition to popularity of online sales of airline tickets, online hotel reservation become widely popular in travel industry and hotel revenues generated through online channels keep increasing (Marcussen 2008). According to a study by Google and OTX published in 2011, internet provides platform for prospective customers to learn experience of other travelers in addition to be the leading tool and the source for researching and booking travel. T he report finds that 45% make personal travel plans and 54% make business travel plans based on reviews and more consumers are submitting their own reviews.