Howie Jacobson, author of AdWords for Dummies, asked me about the SEO implications of aliasing multiple domain names to one IP address as a workaround for Google's new AdWords rule change. As of April 1st, Google no longer allows a display URL in your Google ad if it redirects to a different domain name.

This rule change is unfortunate, as it restricts search marketers' ability to A/B test different domain names in their Google ads. So if you wanted to test www.widgetshelp.com versus your main URL of www.widgetsllc.com, you'd need to remove the redirect from www.widgetshelp.com. Thus you'd have a CNAME or A record in your DNS server for widgetshelp.com, and you'd have a "ServerAlias www.widgetshelp.com widgetshelp.com" line in your Apache config.

But without a redirect, search engine spiders won't know which URL is the canonical one. Widgetshelp.com and widgetsllc.com would look like duplicates of each other, and the link juice to each URL would be split up rather than aggregated together. This becomes an issue when there are links to the alternate domain, as the spiders will find that duplicate site. By the way, don't worry about spiders following the link in the Google ad, as that is not a spiderable link.

Unfortunately the "Preferred Domain" tool in Google Webmaster Central is not going to be a help here, because it only lets you select between www vs. non-www. You can't specify multiple domain names -- at least not yet. Back in 2006 I recommended to Google that they Extend their canonicalization feature in Webmaster Central. Even though they haven't heeded my request, I'm still hopeful that they someday will.

In the meantime, there's a gray hat solution you could implement -- a conditional redirect that only spiders see. It's not without risks, however. You have been warned.

Alternatively, you could contact the site owners who have linked to your alternate domains and ask them to update the link to your main URL. That can only really work if you only have just a few links pointing to your alternate domain. And obviously, don't link to your alternate domain yourself!

We've all experienced frustration trying to print out an important web page or form. Some web designers have felt our pain, creating duplicate pages that are "print-friendly." Unfortunately, these duplicates aren't great for SEO, as the search engines get confused trying to determine which version of your content to serve up to searchers in their results. There are other negative effects as well, depending upon the size of your site and how you've structured it. For example, in my article at CNET I highlight this scenario:

For example, let's say that you have a Web site that has 1,000 pages, a small to moderate-size site, depending on your perspective. Now, because you've taken advantage of your CMS' ability to automatically create a "print this" link on each page to a printer-friendly version, for all practical purposes, your site just doubled to 2,000 pages. But what if your PageRank isn't high enough to warrant very rapid spidering? It could take a lot longer for all your pages to get indexed.

For more about this unique situation, and solutions on how to avoid potential duplicate content issues, read my blog post on CNet: Searchlight.

I had the distinct pleasure of spending an hour on the phone with Vanessa Fox, Product Manager of Google Webmaster Central, interviewing her just over a week ago. Our discussions ran the gamut of SEO issues -- redirects, duplicate content, AJAX, Flash, PageRank, and of course, the wealth of tools and reports that Google has made available in their Webmaster Central.

The interview has been edited down to 40 minutes and is now available for download:

Download / Listen to the interview » (MP3, 9 megs)

Vanessa will be speaking at two of the upcoming American Marketing Association one-day conferences, titled Hot Topic: Search Engine Marketing. Her colleague Amanda Camp will be speaking at the other one.

I will be conducting interviews of all the illustrious faculty of search marketers over the coming weeks, so be sure to subscribe to the RSS feed to get these podcasts delivered directly to you automatically as they are published.

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These conferences present a unique opportunity to hear -- in a small intimate environment with dozens of delegates instead of hundreds -- the latest tips, tricks, tools, trends and best practices from Googlers Vanessa Fox or Amanda Camp along with search marketing practitioners and gurus Eric Ward, Neil Patel, Alan Rimm-Kaufman, Chris Smith (SuperPages.com), Paul O'Brien (HP) to name a few. :-) Oh, and I'll be speaking too, as well as chairing the events.

Mark your calendars: April 20 in San Francisco, May 25 in NYC, and June 22 in Chicago.

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Hope to see you there!