If you are a content publisher or you are an affiliate, you have probably had the painful experience of dealing with your sites getting added to Google’s supplementary index. In essence, the supplementary index is the more like the place between heaven and hell (if you consider main index the heaven). The supplementary index as Google described it was a secondary index that allowed users to search beyond the main index to find content. Unfortunately, the SI sites were not crawled as often as the sites on the main index. In reality, a site that was in the supplementary index was as useful as a banned site. You don’t get crawled as often, and you don’t exactly show up on the early pages of Google. Sites that were added to the SI were deemed to be irrelevant.

So how do you know if you are in the Sup Index? It’s really easy. If you type your domain on Google and search for it (e.g. xyz.com), and you don’t show up on the first couple of pages, there is a good chance that you are either banned or in the SI. You can use the command Site:Domain  to figure out if you have any pages indexed by Google. If you are indexed, then it probably means that your site has been deemed irrelevant by Google. Thin affiliate sites often end up in SI (Google actually has stopped using the term Supplementary Index). But if you are smart about it, you shouldn’t really end up there unless you do something nasty.

Here is how:

• Make sure you have your main keywords on your page. Speard them around your pages, and use proper tagging such as <strong> or <i> to highlight your most important words on each page.
• Make sure you do proper internal and external linking to let Google know why your site is relevant to your main keyword.
• Don’t over optimize your pages. Make sure you watch the keyword density. Don’t make everything bold or anything like that. Google would not like it.
• Don’t add too much content in a short period of time. Many people think that the more content they add to their site the better. While that’s true, you should do that in moderation. There are a lot of people out there who love to take shortcuts. If you add 100s of pages of content to your site, all of a sudden you become a suspect.
• Watch out for duplicate content. Duplicate content almost always gets you in trouble. Whether its ranking drop or complete site exclusion, you want to make sure you avoid putting duplicate content on your pages. Blogs often get into trouble for this issue (due to their architecture), but Google is getting good at recognizing blogs and just ignoring the duplicate issue with them.
• Use Google analytics and Google Webmasters tool to find out what’s exactly wrong with your pages, and how you can fix them. I have probably said this before, but Google tools are almost always the best friends that you can have in the SEO world.

If you provide quality content and don’t take shortcuts, there is a good chance that you won’t have to deal with the SI. But if you are ever in trouble with Google, just follow the above steps, and allow Google time to get you back in the main index. As long as you are not banned for doing something serious, you should find your way back to Google index in no time.