Despite what it says in the Google help pages:
...the Backward Links function does not show every link.
This does not mean that Google is not aware of the links that are
pointing to your site, just that it doesn't list all of them when you
use the Backward Links function.
AlltheWeb has a backward links function that shows every link (of the
sites indexed by AlltheWeb). Just enter a URL in the search box, and
the results page has a link that says:
"Find all external web pages that link to.."
Compare the results of links to google.com provided by each engine:
Google says google.com has 318,000 backward links
AlltheWeb says google.com has 18 million backward links
With Google, try to search for a phrase that should appear uniquely in
links to your site, such as "Marketing the Mousetrap". This sometimes
Consensus of webmaster opinion
At WebMasterWorld there are literally hundreds of discussions about
how the backward links function works.
Almost always someone chimes in with the PR4 factoid:
"Remember that Google only lists pages with a pr4 or higher in the backlink"
"Google shows only backlinks with a pr4 or higher."
"pages with a PR of 3 or less are no longer showing up as backlinks"
The problem is that no-one except for Google search engineers knows
for sure how it works, we can only guess. While the PR4 rule seems to
apply most of the time, there are exceptions. I found one page with
PR4+ that was linking to your site:
Because Link Partners is a reciprocal link scheme (against Google
policy), there is a high chance that Google ignores the links on that
site. To remain within Google guidelines, and the probable guidelines
of other search engines in the future, I suggest that you refrain from
reciprocal linking, as it undermines the quality of search results,
and could result in your site being penalized.
"Don't participate in link schemes designed to increase your site's
ranking or PageRank."
If Google has indexed the pages that link to your site, then Google
knows of the links.
Whether Google assigns importance to links from pages with a low
PageRank is anyone's guess. All you can do is strive to get more
genuine links from sites with high PageRank, which is probably the
most difficult task for any webmaster looking for good search engine