I followed your instructions, the following days, my site tranzen.ca
got listed high up on the keywords (balanced scorecard consulting, zen
management, telecom network services). But now, a week after, I went
back to google to find that my site disappear altogether, whatever
keywords I used, I am not listed. Even when I type "tranzen.ca" I had
5 listing before, now there is NONE!  Why?

Hi again, vietzen!

What you have experienced is most likely the effect of the "Freshbot".

Since your Question was posted just after the end of the latest
completed Googlebot crawl of the web (also known as the "Dance"), it
will be 4 to 6 weeks before the next crawl occurs. For the interim
periods, Google has developed a baby crawler known as the "Freshbot",
which is used to crawl URLs that have just been submitted, as well as
sites that the Googlebot has identified as ones that are important,
contain valuable information, and should be crawled more often than 4
to 6 weeks.

According to the GoogleGuy in a post on WebMasterWorld (October 27,
2002):
"...no promises about where your site may or may not be listing, but
your question is the perfect one to answer about 'everflux.'

If your site is new, or hasn't shown up in Google for long, it may
because our "fresh crawl" (which runs each day) was finding your site
instead of our main crawl (which runs about once a month). Our "fresh
crawl" is a newer feature, and we're still experimenting with which
pages to crawl, how deeply to crawl, etc. We even reserve the right to
(gasp!) not do a fresh crawl on some days because we're doing tests or
reviewing new code. Someone wrote in recently and said "my site got in
Google three weeks ago, and you've dropped me four times!" ;) Nope,
it's just that we don't always crawl the same pages in our fresh
crawl, and we don't always crawl to the same depth. As we do a full
crawl of the web, we find most of the sites from our fresh crawl and
put them in our regular index. My advice on our fresh crawl is to view
it as a nice "bonus" on top of Google's deep index. Users can always
search our full index, but sometimes we can serve up even fresher
pages as an extra nicety. :) "
http://www.webmasterworld.com/forum3/6339.htm   

I hope that this information Answers your Question completely. You
just need to be patient for a month or two, while your site settles
into its regular place in the full Google index.

Before Rating my Answer, if you have questions about the above
information, please post a Request for Clarification, and I will be
glad to see what I can do for you.

I usually keep an eye on the websites of my Customers, so I will be
looking forward to seeing your site do well in Google Search Results.

Best Wishes!

ace

This is what other experts told me as well. So we are really at the
mercy of the system. I started to submit quite a few months ago, still
having to be patient. Thanks a lot your your answer, you are very
thorough. Many thanks.