Apart from this, they also struggle to technically rank websites when there is duplicated content. Who is the authorative website? Who owns the content? Where did the content appear first? These are many of the questions that can’t be answered when duplicated content exists, hence the search engines will negatively rank the pages in question wherever they are found.
Don’t get caught out by this. It’s really easy to avoid and ensure you keep building your SEO levels nicely – simply make sure all your content is 100% unique. If in doubt, you may want to do a few searches for various words and patterns of words in various search engines and see if there are any other matches out there. Check them out and see if they are exact matches of your content.
If this is another website that has copied your content – contact them and make sure they remove it. Explain to them that duplicated content is bad news for both your website and theirs! Then also within your own website, just make sure each page is completely original and nothing has been duplicated from other pages. If you’ve built a new website to replace an old website, make sure you don’t have both online at the same time! Take the old website offline as the new website launches, and create 301 redirects from the old site to the new one.