Composer cannot edit HTML framesets, or pages with inline frames. For framesets, try editing the page for each frame separately. For pages with iframes, save a copy of the page and remove the <iframe> tag.
Impossibile rediger ensembles de quadros HTML o paginas con quadros integrate. Pro ensembles de quadros HTML, prova rediger le pagina separatemente pro cata photogramma. Pro paginas con quadros integrate, salva un copia del pagina e remove le <iframe> tag.