Today I was doing some research on my domain name and I found that half of my posts are in “Supplemental Result”.
If you already have a blog I am sure you’ll find lots of your pages in the “Supplemental Result”. Some people argue that “supplemental result” doesn’t affect the ranking in the search engine.
When a page is tagged with “Supplemental Result” this means that it’s less trusted most of the time because of duplicate content. But I am 100% sure that most of my posts are original and also my writing style is so bad that nobody wanna copy - just kidding .

So I did some research and found out that it could be from the way the links and pages are organized on the blog. For instance, every-time I write a new post, it becomes duplicated somehow on the blog by adding excerpts in the Home page, feeds and in category pages.

So how to get out of the “Supplemental Result” index?

I’ve read in Linkrain blog in this post that editing the robot.txt may help to solve this problem. The way this works is by changing the robot.txt file you can disallow (or allow) search engine robots to index some areas in your blog.

With (www) or without the (www)

Other interesting thing you should know about “Supplemental Result” is that having (www) in your domain is treated differently than not having it when indexed by the search engines.
That’s mean if you have a page indexed first with (www) and then, the SE indexed the same page without the (www) than the later becomes “Supplemental Results” although both pages are the same but they are considered 2 different pages with the same content.

Here is an example:
With (www), my homepage is in the “Supplemental Result” index.

Without the (www), the home page is indexed fine.