The web-based application by VoiceXML service on the Internet is gradually accepted for human-machine interaction because it provides the speech-enabled functionality and makes the telephone access a reality. However, it is not cost efficient to build voice only stand-alone web implementation and is more reasonable that voice interfaces should be retrofitted to be compatible or collaborated with the existing HTML or XML based web applications. Therefore, this paper considers that the functionality of the web site should enable multiple access modalities so that human beings can perceive and interact with either visual or speech response simultaneously. Under this principle, our research develops an integrated web based Mandarin dialog system which adopts ASR, TTS, VoiceXML browser, and VoIP technologies to create user friendly interfaces of GUI and VUI. The users can use either traditional telephone, cellular phone connection, or even VoIP by personal computer to interact with the VoiceXML server. In the mean time, the users browse the web and access the same content. The prototype system shows excellent performance and can be easily implemented into e-commerce ordering service for wide accessibility.