1. At a computer system including an editor having a text view and a design view for editing documents, the text view configured to receive text representing instructions of a mark-up language, the design view configured to interpret the mark-up language and to render corresponding output, a method for automatically synchronizing the rendered output of the design view with an incremental change made in the text view, the method comprising: an act of storing a text view of mark-up language instructions of a document in a text view buffer; an act of detecting a change in the text view of the document; an act of identifying the type of the detected change from among inserting, deleting, and changing text; an act of identifying a change start location of the detected change within the text view buffer; an act of identifying a change end location of the detected change within the text view buffer, the portion of text between the change start location and the change end location representing the excise region of the changed text that is to be synchronized in the design view while preserving the existing characteristics of other mark-up language in the document; an act of inspecting the text view buffer from the start change location towards the beginning of the text view buffer to identify a scope start location; an act of inspecting the text view buffer from the change end location towards the end of the text view buffer to identify a scope end location, the portion of the text view buffer between the scope start location and the scope end location indicating a scoped output region; an act of determining that it is safe to use incremental parsing in the excise region of the document based on the contents of the scoped output region; an act of accessing mark-up language corresponding to the excise region of the document; an act of inserting the accessed mark-up language into the excise region of the document; an act of transferring the accessed mark-up language to a design view parse tree used by the design view to render the document such that the detected change is synchronized between the text view and the design view; and an act of rendering the design view parse tree to represent the detected change from text view within the design view.