Sidenote: If you don't believe there's a duplicate content penalty then another reason to not have the exact same content would be because if 100 people before you put the content on their site they were indexed first and will most likely rank much higher then you for the same thing. No ones going to page 100 to find your copy of the same content.

Ok, so you can do the above but those aren't the 5 ways I was refering to in the subject. In fact I'm talking about going beyond this.

Why? Because, you may be thinking duplicate content is an apples to apples comparison of two websites for the same content and if there's enough percentage different then it won't be duplicate content.

This is NOT 100% true. In fact it's not 50% true.

There is no percentage threshold to say what will be considered duplicate content.

Why? First remember these search engines index and crawl billions of PAGES. They aren't comparing one or two pages to each other. They are taking a sampling of data from many many sites and comparing them all.

They check things like... 1. File Name 2. Directory Name 3. Domain Name 4. IP Addresses 5. Incoming Link Text

You can see what the spider actually takes from your site by going to google and typing in site: www.mysite.com and then clicking on the "cached" link at the end of the listing and then click "cached text" at the top of the page that loads.

Google claims to do about 100 different things to determine a pages listing result (PageRank, Keyword Density, incoming links). So to end up with duplicate content you're going to have to set off more then one flag.

And there are a few other factors to consider. Such as the first part of the page as being more important than the lower content.

I feel this is one of the most overlooked aspects to duplicate content. The idea that what's near the top of the page is the most important to visitors and the search engines.