javascript TextRange boundingLeft, boundingTop

Return the pixel distance between the top or left of the browser window or frame and the top or left edges of the imaginary space occupied by the TextRange object. Although you do not see a TextRange object in the document (unless a script selects it), the area of a TextRange object is identical to the area that a selection highlight would occupy. Values for these properties are measured from the fixed window or frame edges and not the top and left of the document, which may scroll out of view. Therefore, as a document scrolls, these values change.