Don't duplicate content on your site

One trick that spammers like to use is to create one page and then post it in numerous locations, both on one domain and on others. The idea is that if there are enough copies of the page, it will get seen by more people. But search engines don't like duplicate content as it's a waste of space on their servers and does not provide good information to their customers. If a search engine suspects your site is spamming them with multiple copies, your site could be banned.