I have a GoDaddy hosted account and read recently in the Google Webmaster Discussion Group that members were being advised not to use the default 404 page in GoDaddy as this might be seen as duplicate content. What are your ideas on such and should I use my own 404 missing page? Following is the quote from a G employee who frquents those boards.
"4) Get custom error pages. One of the sites in question returned an error page for awhile: "We're having server trouble, please stay tuned." However, other sites hosted by the same hosting company were also returning that same page (it looked like a template error page provided by the hosting company). Since we saw that same content on more than one URL, we ended up only indexing one version of it, and (to the dismay of the webmaster who reported it here) it wasn't his version. "
[edited by: engine at 2:52 pm (utc) on Nov. 28, 2007] [edit reason] formatting [/edit]
What matters is not the page's content, but the actual http status code returned in the servers header. If it is a 404, then the content is not indexed and there can't be a duplicate problem. It couldn't be a problem, since any bad url would return that content.
The thing to be aware of is custom error solutions that return a 302 redirect code to get to the custom content. That can be trouble.
While Tedster is right, what you should care about is the HTTP response, I would like to point something, which is that Google actually indexes 404 pages in some circunstances (sorry as this could seem a bit off-topic)
I have a client with a programming problem, which makes 1 page response to be 404 but to actually return the proper content (the page exists). This page is not only indexed, it also has pagerank.