Having submitted my site www.ppatrainng.ie before christmas, I've been
waiting patiently for it to appear in the Google index, and yesterday
(Jan 21), BINGO! there it was, ranked at the top of the first page on
just about all my keyword searches (QuarkXPress training, adobe
framemaker training, adobe pagemaker training, coreldraw training
etc). I was delighted as you can imagine.

My delight was short-lived however. The same searches today failed to
find my site at all using any of the keywords that were so successful
yesterday. I've tried the search several times, always on
www.google.ie and with the "Pages from Ireland" option checked - the
same way that produced those remarkable results yesterday.

How can I be included in the index so successfully one day and
banished totally from it the next?

greetings, chriso!

Webmasters will frequently notice fluctuations in their Search Results
rankings. This can occur for a few different reasons, and it has been
the subject of much speculation and research by Webmasters.

The Googlebot does a massive crawl every 4 to 6 weeks, indexing the
entire web. This has been dubbed "The Dance" because website Page
Rankings and Search Results tend to bop around a bit while it is going
on, yielding strange, unexplainable variations from one moment to the
next.

Copies of Google's site index (what your search terms are applied to
when you click the "Google Search" button) are located on a number of
different servers, and each of these copies of the index file can be
updated at a different time, and so they are not always synchronized.
Depending on which server happens to be assigned to deliver the
results for a particular search, again, the results can vary.

When webmasters submit their site's URL, it gets added to a list of
"make a special point to go out and check this site" URLs. These URLs
will be indexed first by the "Freshbot" which does a "fresh crawl"
most every day; hopefully, you will notice results within less than a
month of submission because of this. The Freshbot is a separate spider
designed to do only partial crawls -- of just the sites on the list of
submitted URLs and other pages the Googler has deemed worthy of more
frequent indexing  -- so it theoretically gets through its list much
faster than the regular Googlebot gets through the whole World Wide
Web, then starts over again. The Freshbot index gets merged in with
the Googlebot for searching. But again, depending on which server
happens to get the search request, a website may show up in a Search
at one point, but not show up in the same Search done at a different
point in time. And if the Freshbot doesn't visit your site again
within a few days, it may drop out of Google's Search Results again
for awhile.

Furthermore, while the Googleys are not terribly forthcoming about the
secret algorithms used by the Googlebots, it has been noticed that the
country-specific Google Home Pages will frequently show different
results for the same search, due to differences in how the Googlebot
indexes sites with country suffixes such as .uk, .fr, .ca, .ie, etc.

Right now, a search on ://www.google.com for your website turns up
quite a few pages, so we know that the Googlebot has actually indexed
it:
://www.google.com/search?q=%22%2Bwww.ppatraining.ie/%22&num=100&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&filter=0

as it does on ://www.google.ie :
://www.google.ie/search?q=%22%2Bwww.ppatraining.ie/%22&hl=en&lr=&ie=UTF-8&oe=UTF-8&filter=0

This is good news. It means that you have fallen into the Googlebot's
sphere of influence, and your site should be showing up more
consistently, possibly after the next Dance, but almost certainly by
the completion of the Dance after that.

So what you need to do is be a little patient and hang out for awhile,
until your website has a chance to settle in and get comfy in the
Googlebot's index.

In the meantime, there are some other things you can do to help your
website:

1) Submit it to a DMOZ (Directory Mozilla Open Directory Project)
category at http://www.dmoz.org (if you haven't done so already). For
your website,
Computers: Internet: Training: United Kingdom  
http://dmoz.org/cgi-bin/add.cgi?where=Computers/Internet/Training/United_Kingdom
seems to be a likely choice.

2) Submit your site to other Search Engines (if you have not done so
already):
  HotBot:   
http://ldbreg.lycos.com/cgi-bin/mayaLogin?m_PR=29&m_CBURL=http://insite.lycos.com/searchservices/lite?step1.asp
  AllTheWeb:   
http://www.alltheweb.com/add_url.php   
  AltaVista:   
http://addurl.altavista.com/addurl/new   
  Zeal (LookSmart/MSN free submission w/free registration)   
http://www.zeal.com/users/register.jhtml   

3) Learn more about how the Googlebot and other Search Engine Spiders
work by visiting Webmaster resource sites. Probably the best one of
these is WebMasterWorld, at http://www.webmasterworld.com . You can
use their Search function to look for forum discussions on subjects of
interest to you, such as "Page Rank" and "Freshbot", or you can just
browse through the forums, clicking on postings with interesting
Subject lines.


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

I hope that this Answer has provided you with exactly the information
you needed -- Best Wishes for increased traffic to your website!

Regards,

aceresearcher

Many thanks - I think you have told me exactly what I needed to know,
and it seems likely that the lack of synchronisation between the
Google site index servers is the problem. I have already submitted to
DMOZ and the others you mentioned, so I guess I just have to play the
waiting game a little longer!