Matt Cutts talks about links, reputation & rankings...

A link is like a vote (see Google's explanation). Because if I link to your site, it generally means I endorse it.

Search engines weigh up all the links on the web, and calculate the relative endorsement of each page.

How to check link juice

  1. Download the Google Toolbar

  2. Ensure that it displays the green PageRank bar

  3. Go to any web page and check the PageRank of that page, bearing in mind that this green bar perfectly represents Google's calculation of that page's level of linkjuice-based authority from some time within the past few months. Indeed, the Toolbar PageRank of each page gets updated roughly 4 times a year, so can be upto a few months behind the real-time PageRank authority that Google uses to deliver search results, and this delay occurs in an effort to prevent spammers from analysing their own success.

Direct Inlink Count

It would be very simplistic, but still a useful indicator, to check the quantity of direct inlinks (inward-bound links, pointing directly to your page) as a measure of your page's general importance.

Example 1: UK Political Parties

For example, if I wanted to find out the order of popularity between the main UK political parties, I could check inlinks (also known as backlinks) via Yahoo Site Explorer for a rough indicator. Having just checked (on 4th November 2009), I found:

As you can see, "quantity of direct inlinks" is a very good but imperfect indicator, so we need to extend it. In order to determine the likely, general significance of your web page, search engines doesn't just count how many pages link in to your page; they also check how many pages link to each of the pages that link to you, and how many pages link to those, and so on, to gain a well-rounded view of the importance of your page relative to every other page on the web.

Indeed, links can go around in endless cycles, so we end up with pools of link juice on each page...

And each link from a page with high link juice is like a river that carries a tenth of that page's juice to a given target page.