I think for some fallback mechanisms <object> is the only way to implement them in pure HTML.
E.g. I once built a logo element, where the logo may be either at logo_A.jpg, logo_B.jpg or logo_C.jpg. As there wasn't any API to determine which of them would exist in advance, I instead used three nested <object> tags. They would request the image in sequence, and the first one that would respond with an image is displayed.
E.g. I once built a logo element, where the logo may be either at logo_A.jpg, logo_B.jpg or logo_C.jpg. As there wasn't any API to determine which of them would exist in advance, I instead used three nested <object> tags. They would request the image in sequence, and the first one that would respond with an image is displayed.