Originally Posted by Webnauts

Martin, IncrebibleHelp would confirm that I posted such a list about supplementals many times here the last two years, but never got credited that way. I am just wondering why?

Here is mine once again:

• Pages due to canonicalization problems, e.g duplicated content, too much content similarity;
• Pages with low or no content;
• Orphaned web pages. Pages that no one links to, including your own;
• Error pages, if a site does not use If-Modified-Since, Last Modified and/or Expires rules;
• Poor website navigation;
• Loading pages with irrelevant keywords (keyword stuffing);
• Too low PageRank;
• Long URLs, especially with long parameters, starting with a question mark (?) and being separated with an ampersand (&amp and are not rewriten;
• Suspicious pages for spamindexing, like non-unique and irrelevant to page content heading tags, meta tags, or linking to bad neighborhoods, etc;
• Too low PageRank.

Check how many of your pages are in the supplemental results with this tool: Supplemental Index Ratio Calculator