Abstract: The inventive editor allows web authors to edit HTML visually while preserving the HTML source document. The editor preserves the structure and format of the HTML, and permits simultaneous modeless visual and source document editing. When an edit is made with the invention, only the HTML source around that edit is updated, rather than rewriting the whole HTML source document. Furthermore, when an edit is made, the new HTML source code is outputted in a format that is specified by the user. In order to preserve the format of the document, format information is stored in the parsed tree. The format of the node is preserved when its source is regenerated; edits to the node will reformat it according to user preferences. In order to preserve the structure of the document, invalid HTML structures are maintained and not corrected.