I started on a serious search to find the best information on Google supplemental index (SI) related to WordPress and found a lot of people (most) are just throwing out theories. They are creating plugins with, in my opinion, no real understanding of the issue and why Google puts WordPress pages in the SI.
One guy has been flaming me about how crappy our WordPress-based product is like it’s our fault. (Hey David, you can stop now. I get the point – you’re clueless. Let’s leave it at that.)
What I learned from my extensive reading on the subject from a gazillion bloggers, garage SEO bands, and the “top” SEO guys is no one knows what they are talking about. Everything is contradictory and everyone has an opinion based on theories, not fact.
So I went to the source. The “voice of Google” who has some of his own pages in supplemental results. Yeah…even Matt Cutts has supplemental results.
Here’s what he said in his latest post on the issue, Infrastructure Status, January 2007:
As a reminder, supplemental results aren’t something to be afraid of; I’ve got pages from my site in the supplemental results, for example. A complete software rewrite of the infrastructure for supplemental results launched in Summer o’ 2005, and the supplemental results continue to get fresher. Having urls in the supplemental results doesn’t mean that you have some sort of penalty at all; the main determinant of whether a url is in our main web index or in the supplemental index is PageRank. If you used to have pages in our main web index and now they’re in the supplemental results, a good hypothesis is that we might not be counting links to your pages with the same weight as we have in the past. The approach I’d recommend in that case is to use solid white-hat SEO to get high-quality links (e.g. editorially given by other sites on the basis of merit).
That’s about as clear and sensible explanation of supplemental results as you are going to find anywhere on the web from an authoritative source. Surprise, surprise, it’s all about the links. Deep links. Most people go find links to their home page and think they are doing all they can do to improve their rankings.
The other important note is “on the basis of merit.” Meaning you have to have content people link to “editorially” of their own free will, which means you have to have good content. Good, original content.
After that, if you have pages in the SI, check what backlinks they have and see if any PageRank has transferred to them yet, and you’ll have a better understanding as to why they are in the SI.
Get them linked or let them sit depending on their value to you having traffic hit them and being ranked.
And then be done with it. Don’t waste a lot of time trying to get old pages out of SI when you have a lot of other marketing and writing to do. Going retroactive on your Google search engine marketing to a high degree really has diminishing returns when you consider that time is much better spent on new content and new traffic sources and links.