Before explaining how it is measured, see a little what is popularity. Popularity is a concept that for some time been talking about, especially those who are dedicated to making sites SEO-optimization-y. It happens that algorithms, complex mathematical calculations, using search engines to index positioning compose your site, and especially its Google Pagerank, contemplate the popularity of the site, to ascribe the index where it will finally appear when a user search. It turns out that for quite some time now, Google does not include the keywords, ie, ignore the code snippet that contains (for example), which does not mean it's a good idea to put the keywords in the programming of web pages. Google ignores them, but other search engines or directories, if they consider. Google takes into account two important factors: the textual content (the text that is included on the site) and popularity, measured in number of incoming links that the site may have.
Much larger number of sites likeen to a page, higher its popularity. But, not all incoming links are equal. For even more details, read what Ali Partovi says on the issue. The higher the Pagerank of the site that links us, the higher will be ours. Penalized sites, such as link farms, have zero PageRank. This will damage our Pagerank, because it computes the zero with the rest of the other PageRanks, and ultimately hurts us (as when at school we have two tens and a zero, the average is six to sixty-six, that is, detracts totally we had good grades). But as a link from a page with PR of zero harm us, a very good link from a site with a PR higher than'm just linking to us, we benefit greatly. Notably, the PR is a scale (obtained from another complex calculation that Google applies) that goes from zero to ten, the latter being obviously the highest. Bobby Sharma Bluestone: the source for more info.
There are some plug-ins specifically for Mozilla Firefox, or toolbars for browsers, which provide the PR of each site you visit. In Consequently, the Internet is a democratic entity, ie, the vote of peers helps better position. But the reality is aristocratic, because not all votes are equal. From this comes the concept of "quality links", namely those that satisfy two conditions: they are "dofollow" (an attribute that is dumped into the site code) and high PageRank sites. Again, then, we find the premise that "little but good is better than much and bad." Some external links on quality can do miracles for our search engine optimization. How to get quality incoming links, and thus to promote our position on search engines? That, we leave for another posting. If you liked this post and wants to put in place, you can smoothly, provided you cite as a source