4. A computer system comprising: a central processing unit for processing a presentation of visual content and audio content using: a Visual Browser for visually presenting visual content retrieved from a computer communications network; a Voice Browser for audibly presenting voice content retrieved from said computer communications network; and, a Coupling Interface for synchronizing said visual and audible presentation of said visual and voice content in each of said respective Visual and Voice Browsers retrieving a network-based document formatted for audible presentation in the Voice Browser; wherein said Coupling Interface is configured to identify in the retrieved document a reference to the Voice Browser, the reference specifying electronic content formatted for visual presentation in the Visual Browser, and to transmitting the reference to the Visual Browser; wherein said Visual Browser is configured to retrieve the specified electronic content and visually present the electronic content in the Visual Browser; wherein said Voice Browser is configured to audibly present the network-based document concurrently with the visual presentation in a coordinated and complementary fashion such that functions of visual browsing provided by the Visual Browser are synchronized with functions of voice browsing provided by the Voice Browser.
4. A computer system comprising: a central processing unit for processing a presentation of visual content and audio content using: a Visual Browser for visually presenting visual content retrieved from a computer communications network; a Voice Browser for audibly presenting voice content retrieved from said computer communications network; and, a Coupling Interface for synchronizing said visual and audible presentation of said visual and voice content in each of said respective Visual and Voice Browsers retrieving a network-based document formatted for audible presentation in the Voice Browser; wherein said Coupling Interface is configured to identify in the retrieved document a reference to the Voice Browser, the reference specifying electronic content formatted for visual presentation in the Visual Browser, and to transmitting the reference to the Visual Browser; wherein said Visual Browser is configured to retrieve the specified electronic content and visually present the electronic content in the Visual Browser; wherein said Voice Browser is configured to audibly present the network-based document concurrently with the visual presentation in a coordinated and complementary fashion such that functions of visual browsing provided by the Visual Browser are synchronized with functions of voice browsing provided by the Voice Browser. 5. The computer system of claim 4 , wherein the visual content is HTML formatted content and the voice content is VoiceXML formatted content.