perhaps it would be better to say that it may be hard to tell what software was used, but it'll be easy to tell if software was used, or if a site was hand coded.
sorry for expecting the worse but i'm fairly biter about students cheating on homework. it's about that time when students are given homework (end of half term when it should have been done ages ago etc) to make a website from scratch and then they go out and cheat. I saw this at college and kids were getting a's as they wrote a good contents page whilst i got a b only because my hundreds of pages were not numbered but instead stapled into chapters and then numbered the chapters. buggers!