This article will guide you through the main reasons why pages get listed on this index, and most importantly, how to get them out. If you have an existing site, there is a high probability that you may have pages in the supplemental index, so use this as a reference, and make sure you follow the steps outlined here.
First of all, for those of you new to this topic.
What is the Supplemental Index? Here is the short answer Google has actually 2 indexes, on call the Main Index and a secondary one known as Supplemental. One way to verify that you are looking at a supplemental result is that you can see Supplemental Result in green text on the bottom line of any given Google listing.
Why do pages move from main to supplemental?
There are many obvious, and some not too obvious reasons for this, but Duplicate Content and Non-Updated are the two main ones. A too dynamic url, in other words, with too many variables, or a page that is to deep in the sites structure also accounts for this. A word of advice on linking: If you are doing excessive reciprocal links, link buying/selling or linking to spammy neighborhoods stop! Google algorithms has very low trust in...