Meanwhile, the link spam began. People chasing higher PageRank scores began dropping links wherever they could, including into blog posts and forums. Eventually, it became such an issue that demands were raised that Google itself should do something about it. Google did in 2005, getting behind the nofollow tag, a way to prevent links from passing along PageRank credit.

Most online marketers mistakenly attribute 100% of a sale or lead to the Last Clicked source. The main reason for this is that analytic solutions only provide last click analysis. 93% to 95% of marketing touch points are ignored when you only attribute success to the last click. That is why multi-attribution is required to properly source sales or leads.
The first component of Google's trust has to do with age. Age is more than a number. But it's not just the age when you first registered your website. The indexed age has to do with two factors: i) the date that Google originally found your website, and; ii) what happened between the time that Google found your website and the present moment in time.
9. Troubleshooting and adjustment. In your first few years as a search optimizer, you’ll almost certainly run into the same problems and challenges everyone else does; your rankings will plateau, you’ll find duplicate content on your site, and you’ll probably see significant ranking volatility. You’ll need to know how to diagnose and address these problems if you don’t want them to bring down the effectiveness of your campaign.

Page Ranks Denver