Since the arrival of Penguin 5 there is a great deal of interest in understanding what a low quality backlink is : specifically what Google ‘thinks’ is a low quality backlink.
Google defines broadly defines low quality backlinks in its WebMasters Guidelines in the Link Schemes section where they refer to these as:
- Buying or selling backlinks
- Excessive Link exchanges
- Large scale article marketing
- Automated programs to create links
Google also provides a range of examples of unnatural backlinks including:
- Text advertisements (without a no follow directive)
- Advertorials or native advertising where payment is received for articles (without a no follow directive)
- Links with optimized anchor text in articles or press releases distributed on other sites.
- Low-quality directory or bookmark site links
- Links embedded in widgets that are distributed across various sites
- Widely distributed links in the footers of various sites
- Forum comments with optimized links in the post or signature, for example:
My interpretation is:
- Backlinks from advertiser sites that do not include a no follow tag
- Backlinks from low quality sites eg sites that are clearly just a backlinking farm
Ironically backlinks that may have helped your website rank prior to Penguin 5, may now be the cause of its non-performance.