In the beginning, search engines were crap. I don’t mean to knock the pioneers, but they simply relied too heavily on what webmasters said their websites were about. That’s why porn sites ranked for searches like, “the whitehouse.” People are shameless – if they can scam their way into money, you’d better believe they’ll do it. Follow the incentives. When Google came onto the scene, touting founder Larry Page’s new PageRank metric, things changed. PageRank was a way to measure websites not by how relevant their webmasters said they were – but by how relevant and authoritative other webmasters said they were. Since then, links have been central to getting sites to rank in search results. It’s nearly impossible to rank without them. PageRank is definitely not a tell-all metric, but one of its core theories still holds true: Not all links are created equal. If you’re getting into the SEO game now you probably already know you need links to rank. And you’ve probably been run through the gamut on how you can build/attract them. This post assumes manual link building (i.e. everything other than linkbait) is at least part of your strategy. Link metrics essentially answer (or attempt to answer) this question: how strong is the page where the link will be published? The stronger the page, the stronger the link it passes. What follows is an introductory guide to metrics we can use to evaluate links. PageRank To learn the basics of PageRank it’s a good idea to read Larry Page and Sergey Brin’s thesis paper, The Anatomy of a Large-scale Hypertextual Web Search Engine , from their PhD work at Stanford. Yes, it’s academic writing, so you may want to stab your eyes out with a pretzel at some point, but this document formed the basis of one of the biggest technology revolutions in modern history, so buck up. Alright, I know probably 95% of you won’t read the paper – so have a look at this graphic. It gives you the basic idea. (Arrows represent links.) Things have changed since PageRank was first conceived (quite a bit), but the basics are still in play. PageRank is basically a 1-10 score for a page based on how many links it has (and how strong those links are). It’s logorithmic, meaning it’s 10x harder to get from 2 to 3 as it is to get from 1 to 2. It generally follows that the higher the PageRank of a particular page, the more PageRank (or “link juice”) that page can pass to other pages through its links. While most SEOs worth their salt will tell you to ignore PageRank, they still secretly check it when nobody’s looking. How can you collect PageRank data? With a toolbar ( Google Toolbar , SEOQuake ) With live SERP displays ( SEOmoz Toolbar does it , SEOQuake ) mozRank & mozTrust (from