Images and copy go without saying.
Original authorship is the keyword that might not hold up in court since most sites have designs based on another. From reading above, you’re implying that once you create a site, you can slap a copyright symbol on there and that protects you from someone else using your layout. So what I’m saying is, how can you prove you didn’t copy some of that code which doesn’t necessarily make it originally authored by you.
You might be thinking of Trade Dress which still may be hard to prove.