Alternative domain names for same site: mask or redirect?

[Moth3r]

I set up a simple website for a friend who runs a small business.

He has two domain names: one is the official name of his company, the other is a "short" version that most previous customers refer to him as.

At the moment the site is hosted on the main name, and the short name is just a forwarding domain (so it opens the main site in a frame, i.e. domain masking).

I'm wondering if this would adversely affect search engine ranking (for example, does it fall foul of Google's "Duplicate content (http://www.google.com/support/webmasters/bin/answer.py?answer=66359)" guidelines)? Would it be preferable to use a permanent 301 Redirect instead?

[Ecom-host-guru]

For seo its preferable to use a permanent redirect. Otherwise you have 2 potential domain names to rank under and your link popularity can be split, also you have potential duplicate content issues.

[Sarah_]

You should definitely go for 301 redirect. It's much more healthier and you avoid risks. It's also better for the users.

[jacksters]

Of course use redirect, we had such issue and the other domain got sandboxed.