Unremarkable page took over homepage in site:example.com

[1script]

Hi all.

I have this predicament I'm finding one of my sites in: when using site:mysite.com operator, most of the time the #1 result is one unremarkable page on my site and the homepage is only #2. It's always this one page and there is nothing special I can find about this page. There are no external in-links I can find (using Y!) and it's not particularly fresh either (4 years old, in fact). It could not be better linked internally either - the homepage has something like 160,000 external links (GWT data, so it's both do- and no-follow) and it's linked from every single page of the site.

So, why this page has a preference over the homepage? I know the site: operator is notoriously unpredictable/unreliable (throw in "undependable", too :)) . But I find that it does roughly correlate with amount of G* traffic I receive - more pages shows as indexed via site: operator usually (though not always) means more traffic I get.

The only thing I can think of is that there is some sort of an issue with the site as a whole that pushes the homepage back rather than promotes this particular page. Has anyone else observed something similar and if so, does anyone have a theory about what may be causing such behavior.

[tedster]

I've never seen this kind of thing - where the home page ends up at #2 and the search traffic goes down when that happens. But it's an excellent observation for these times of volatile rankings on Google and I'll be on the lookout.

Just as data points:

1. The URL for your home page is the domain root, correct? - just http://www.example.com/ with no redirects for any reason?

2. All your internal links back to home point to your domain root as well, with no added index.asp or anything like that?

[1script]

Well, if we are to use this as a data point, I guess I should provide more detail.

1. During the time that page replaces homepage as #1 on site: search traffic does not go down sharply but deteriorates slowly i.e. if you compare this Wednesday to the last, you'll see 50-100 less visits (or 5% down in a course of a week) from G*.
2. The cache date of the homepage itself behaves VERY weird: for several months now it gets indexed on, say August 15th. Then after 1-2 days the cache date rolls back to August 10th or so and stays there for painfully long time (2-3 weeks at least). Then updates to a fresher date and shortly after that slips 3-5 days back again! Homepage itself updates many times a day (busy forum) and before the problem started in March 2010 never had a cache date more than 3 days old (and often updated a couple of times a day back then).
3. Overall number of pages indexes (as returned by site: operator) also goes down slowly even though GWT shows actual increase in sitemap URLs indexed.
4. The homepage is the root of the domain
5. There are no redirects for www version. Non-www 301 redirects to www
6. I have started using all absolute links (link to homepage included) a couple of weeks ago but this problem predates the change and did not improve / change after the switch to all absolute links.