Domain Name Forwarding and Search Engines

You own a single site, but several domains - perhaps you wanted to make sure that even if your customers misspelled your domain name they'd get to your site, or perhaps you'd like to have a specific domain name direct to a page deep within your site - whatever the case, there are some important considerations surrounding multiple domain names routing to a single site and search engine submission.
Search engines like Google and Yahoo won't always wait around for you to submit a site - Googlebot and Yahoo Slurp (which you may recognize from your server logs if your site has been up for a few weeks) are constantly running across new domain names to index. It's a good thing - unless your domain names are being forwarded incorrectly.
What constitutes and incorrect forward?
Many major domain name registrars offer a "Domain Name Forwarding" feature which, while it may be the easiest way to forward your domain, can cause some real problems when search engine spiders like Googlebot or Yahoo Slurp visit your site.
Here's what happens:
1) The search engine spider pulls your domain name (usually from http://www.whois.sc/ ) 2) The spider visits your website, using the domain name forwarded through your domain registrar 3) Your domain registrar is using a Temporary Redirect (most likely because it's assumed that you'll point the domain name to a new hosting account sooner or later), frames, or other incorrect forwarding method 4) The spider indexes your site
But what went wrong? Your domain name registrar did its job, and sent the spider to your actual site when it visited the domain name you registered. The spider did its job and read the content of the page or pages it found, and then incorporated them into the search engine index. Everything's copacetic, right?
When the search engine spider read the page, it associated it with your alternate domain name, the one that was supposed to be forwarding to your primary domain name. This means that the search engine has effectively tracked down what it will quickly identify as duplicate content - and, after years of dealing with sites trying to sell Viagra on the sly by duplicating their content across hundreds of pages, today's search engines will respond to duplicate content with a drop in your ranking.
Given enough time, you may find your site has been banned from the search engine index.
What's the solution?
Your domain names need to be routed from the domain name registrar to a hosting account - from the hosting account (and this varies - consult your technical support provider for the account) you'll need to set a Permanent Redirect to your main site.
A Permanent Redirect is logged as a code '301' (thence, it is often referred to as a '301 Permanent Redirect') - if you have multiple domain names which you wish to direct to a single site, it may be especially useful for you to consider a website hosting account which offers multiple add-on domains and subdomains to accommodate all the domain names you'll need to forward