The first thing that it is important to point out is that there is no direct penalty from the search engines for duplicate content. However you may find that it will be difficult to get top rankings for it as the search engines only like to show one page with the same content on it.
What is duplicate content?
Basically duplicate content occurs when 2 pages have exactly the same content. However it is also worth saying that 2 pages will be considered duplicate content if their content is similar or overlaps in a number of places.
You will find that search engines will consider web pages from the same website and from different website in order to determine duplicate content. So you need to be very careful when writing the content for your website.
How do Search Engine Treat Duplicate content?
Well basically the search engines try to provide searchers with as many varied results as possible. So basically if they have a duplicate content issue they will need to determine which they think is the original content and this will be the one they will show.
When a search engine comes across a web page it will scan it a usual and then compare it to other web pages it already has in its database. If there is a duplicate content issue then it will need to determine which one it wants to show. It will do this by firstly removing any spam sites as these are not welcome in their rankings. Whatever they have left they will consider the inbound links and rank them based on that. If your content does not have the highest number of links then there is a good chance it won't appear anywhere in the search results.
How to get around Duplicate Content Issues
There are 2 things to consider here, the first is duplicate content on your website and the second is with other websites.
On your own website you might have the issue of having a print version of each of your pages. This can cause problems with the search engines and they might list the wrong version. The best thing to do is to prevent the search engines from indexing the print version which will automatically remove the duplicate content issue on your website.
Now you need to consider your content with other websites and this usually occurs where people distribute content to article directories and similar places. The best way to handle this is to ensure there is a link back to the original content on your website. This will show the search engines where the original comes from and ensure it is your content that is listed.
Duplicate content is something that every website owner should be aware of and if you provide high quality valuable content then there is a chance it might be copied so try and check it out and report any issues that you might have on duplicate content to the search engines immediately.