i built an online travel agency in German for a client which was frames based (circa 700 pages).
It has been up for 3 years and has about 1500 other websites linking to it.
Now the client wants the site completely rebuilt but without frames. My question is, do i leave the old site on the server and redirect with a 301 (if so for how long)? Or do i delete the old site from the server and use a 404 explaining to the vistors what has happened. I do not want to get penalized for duplicate content if i have both site up at the same time.