Duplicate content issues can kill your website. What's "duplicate content?" Well, it's when you say things twice on your website, and say things twice on your website. Duplicate content also occurs when you copy information from someone else's website to post on your own site. Perhaps your intentions were good for your readers, but you didn't realize that copying that diamond education information was bad for you.
Most duplicate content issues occur right on your own website rather than from the blatant copying from someone else's site. Perhaps you didn't mean to repeat yourself, but it does happen. Your website blog could be mis-configured to repeat itself, or you might have a product catalog that spins wildly out of control.
The worst level of duplicate content happens now when your entire website is copied. Although search engines have been dealing with this for years, it wasn't always a big concern. Now search engines are fighting back. Many website programmers and website owners are creating trouble for themselves when they get this wrong and cause their site ranking to be zapped badly.
Let me tell you a story...
When the "World Wide Web" first emerged in the early 1990's the common practice was to show your website with the full URL, which my typical example would be the fake jewelry website "http://www.perosijewelers.com." As web browsers became smarter they would add the "http://" part of the URL by default for you. This made it much easier to give out your website address by simply telling people to go to "www.perosijewelers.com" without spelling out the clumsy prefix of "aitch-tee-tee-pee-colon-slash-slash."
Now that the internet has matured even further it is common to completely drop the "www" part of the website address, leaving only the domain name of "perosijewelers.com." This is where the trouble comes in.
Google is on a quest to clean up the sloppy programming of the internet. Users should be able to view your website regardless if they type in "www" or not into their browser. However, you as a website owner need to decide which version will be "correct" and you need to program your website so that it always brings users to the correct version.
Specifically, if I wanted to use http://perosijewelers.com as my correct website address I would have to make sure that the website automatically redirects all users from the http://www.perosijewelers.com version to the "non-www" version. Actually, my personal preference is to direct all users from the NON-WWW version to the "http://www.perosijewelers.com" version.
Here's where the trouble comes in for website owners... From Google's point of view, the "www" and "non-www" versions of your website are two completely different websites that share duplicate information. At one point they didn't really care too much about this. Google even has a feature inside Google Webmaster Tools that allows you to choose which version of your website you want to be primary: www or non-www.
Full website duplication of the www/non-www became an issue as companies started massive link building campaigns to drive business with very poor website content. As the quality of content was more and more riddled with spam, Google had no choice but to figure out how to fight back. That fighting including zapping website spam that was copied from other websites.
Sadly, the duplicate website issue now falls under spamming.
So how do you know if your website is set up correctly? It's simple; just type your domain name into your web browser with and without the domain name. You should always end up in the same place no matter what you type.
Example:
Typing "perosijewelers.com" brings you to "www.perosijewelers.com"
AND
Typing "www.perosijewelers.com" brings you to "www.perosijewelers.com" --> Good!
Typing "perosijewelers.com" brings you to "perosijewelers.com"
AND
Typing "www.perosijewelers.com" brings you to "perosijewelers.com" --> Also Good!
Typing "perosijewelers.com" brings you to "perosijewelers.com"
AND
Typing "www.perosijewelers.com" brings you to "www.perosijewelers.com" --> Very Bad!
Take a quick look and ask your web programmer to fix this for you.
