When you ctrl+S to save a page, by default the first attempt fails, as evidenced by the warning icon in the Downloads button. You click it again to save it, and

When you ctrl+S to save a page, by default the first attempt fails, as evidenced by the warning icon in the Downloads button. You click it again to save it, and naturally it redownloads and reexecutes the page and all its resources again. Likewise if you save an already open image, more often than not even when it was just loaded, it will need to be downloaded again.