The first two things that come to mind when I hear "doorway" would be:
- A backdoor to a site that will be spamvertised, with hopes that the main site (on another account) won't pay the price.
That would be a no-no here.
- A backdoor to a site that isn't spammed (other than search engine spamming, by most SE's definitions), but is hosted on a separate account. Often nothing more than a link from an IP on a different C-class than the actual site... just looking for links/Google PR.
Number 2 would be harmless, though some search engines can/will see through it, especially if a competitor reports it and you get checked out by an actual human in the abuse department.
If the doorway is just intended to capture type-in traffic, it's a good idea to just use a 301 redirect to the main site. That way, visitors will still find your site and there's no need to worry about a search engine considering it as doorway spam.
Since the poster asked if it was okay, I'd guess he was referring to number one.
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