There’s a lot about this theme already published online, but I think it doesn’t hurt to highlight a few points here, for your information. Why do some web pages go supplemental? For various reasons, but three lead the pack.
- High percentage of similarity among different pages – meaning: if you copy content from other pages, including your own within the same site, chances are that the page found “guilty” of similarity will end up in the supplemental results. High similarity might include but it is not reduced to the same page titles and descriptions.
- Lack of fresh content: the Web is constantly changing. Many webmasters come up with better articles about a certain topic and they cover it so well that everyone will link back to their pages. Thus their pages gain more authority and push your static pages lower and lower in the main index, till your pages will eventually end up in the supplemental index.
- Poor linking strategies.
To avoid the supplemental trap you could certainly perform some onsite optimisation: rewrite your page titles and meta descriptions, take care how you write your content to avoid similarity, use H1, H2, etc to structure your content, interlink the pages with relevant anchor texts and much more. Focus on good linking campaigns to increase the authority of the pages caught in the supplemental trap and when you are all done… wait to see the results. It might take up to three months to save your pages, but the effort is certainly worth. If you want to speed up the process, you can count on SEO Ltd.