1. A tactile access and navigation system for a visually impaired user operating within a computerized data environment, said system comprising: a. a tactile mouse having at least one tactile display and at least one user-operable input control; b. data extraction, analysis and transformation software in communication with said at least one tactile display, operative to extract and analyze display data from the computer, and to transform extracted display data into a form suitable for display by said at least one tactile display; c. means for rearranging GUI elements selected from among the display data into a new hierarchical structure having at least two hierarchical levels, said new hierarchical structure being navigable by jumping from an element in one hierarchical level to an element in a different hierarchical level without regard to their location within the display data by predetermined directional inputs to said tactile mouse; and d. means for providing data to said at least one tactile display in accordance with predetermined modes of operation, which include: i. a viewing mode for displaying on said at least one tactile display a tactile representation of graphical and textual data content; and ii. a navigational mode for displaying on said at least one tactile display a tactile representation of the relative positioning of said GUI elements within said structure, wherein said navigational mode is selected by the user from the group comprising: a. a spatial navigation mode wherein the user is enabled to freely move a fiducial element along a desired path; b. a contextual navigation mode wherein the user is enabled to jump a fiducial element to a new location in response to a predetermined user input via said tactile mouse; and c. a spatial-contextual navigation mode wherein the user is guided to move a fiducial element along a virtual guide trajectory by use of said tactile mouse.