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 323,000 backward links
AlltheWeb says google.com has 16 million backward links
In this instance AlltheWeb doesn't show many links to your site, but
usually it is much better than Google for this purpose.
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. The instance you
mentioned above seems to be the only one - all the other pages I found
linking to yours were PR3 or less.
The PageRank system seems to be restricted to whole numbers between
0-10, but in reality a page could have PR4, PR4.5 or PR4.53876. It is
quite likely that the real cut-off point for showing backward links is
something like PR4.1 - unfortunately there is no way for webmasters to
see more accurate PageRank then the Google Toolbar.
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
Clarification of Answer by
04 Feb 2004 23:44 PST
As I pointed out, no-one really knows how Google decides which links
to list, but in the past PR4+ has been a good rule of thumb.
Check the cached version of http://www.travelbb.com/uk/ and you will
see why it doesn't show up - your link is not in the caced version,
and the cached version represents what it is in the current index.
I have no answer regarding the other one, except that Google has
introduced a filter aimed at stopping sites gaining advantage from
using the same keyphrase in all the links to a page/site. Considering
all the links I have seen use the same phrase (which is normal in my
book), Google might be discounting some of them... It's really hard
when all we can do is guess, and Google keeps changing their
Ultimately nothing has really changed - get as many genuine, quality
links pointing to your site as you can. We will probably never know if
not being listed in backward links means the link is redundant or not.
For example, my business site dropped from PR7 to PR6 last week.
Nothing has changed in terms of links or content, and I run a very
clean ship. Often it is just the tinkering of the Google Engineers.