24. A method for enabling in-context authoring of alternate substitute content for one or more non-textual objects, comprising: accessing an electronic document comprising content data; and facilitating in-context editing of substitute content corresponding to a non-textual object, comprising: selecting a segment of at least part of the content data; selecting one non-textual object from a plurality of non-textual objects contained within a data source; associating the selected non-textual object with the content data segment; substituting the non-textual object for the content data segment; and storing the content data segment as the substitute content for the non-textual object.
24. A method for enabling in-context authoring of alternate substitute content for one or more non-textual objects, comprising: accessing an electronic document comprising content data; and facilitating in-context editing of substitute content corresponding to a non-textual object, comprising: selecting a segment of at least part of the content data; selecting one non-textual object from a plurality of non-textual objects contained within a data source; associating the selected non-textual object with the content data segment; substituting the non-textual object for the content data segment; and storing the content data segment as the substitute content for the non-textual object. 27. A method according to claim 24 , wherein the non-textual object is selected from the group comprising graphics, images, icons, controls, applications, audio output, video output, tactile output, MathML, SMIL and subdocuments.