Deckey on "Internal server error"

I've also another question: in my Host FTP I have the folder "public_html" , but also the "www" with the "?" on the folder.
I've seen that I had the web-site content in both of the folders. Is may a problem?
I've tried to delete from "www", for leave only in "public_html"...but now I reinstalling because the website doesn't work (like as you see 404 error).