Content which is duplicate or near duplicate in nature. Search engines do not want to index multiple versions of similar content.
For example, printer friendly pages may be search engine unfriendly duplicates. Also, many automated content generation techniques rely on recycling content, so some search engines are somewhat strict in filtering out content they deem to be similar or nearly duplicate in nature.
- Duplicate Content Detection – video where Matt Cutts talks about the process of duplicate content detection
- Identifying and filtering near-duplicate documents
- Search Engine Patents on Duplicated Content and Re-Ranking Methods
- Stuntdubl: How to Remedy Duplicate Content