Some thing very strange happened to one of my clients sites today, some thing
I have never encountered before. I tend to believe this is either a glitch in
google's algo OR a penalty (for unknown reasons).

The site was ranking for several terms for a couple of years now. It is an
established portal with a large amount of content and inbound links.

Suddenly today the index page lost all rankings, while inner pages remain quite
the same. The only main difference I can think of is that I've placed a meta
language tag on all pages since I now started building also foreign language
sections. Even though I did that change about two weeks ago.

Once I noticed that the site is no where to be found in Google's SERPs,
I immediately removed the tags. Several hours after I noticed a change:
(Not that I'm implying that the change was because of my actions)

The site again shows for about half of the terms it used to rank. Same positions as it used to.
BUT, instead of showing the title and description, it shows only the URL.

After some more investigation I found some thing very disturbing which I've
never seen before. I can not find the site when doing an allinanchor: search.

Not for the keywords it used to rank and not for the ones It does now.

I've never experienced that issue before and I would love it if some one can
share his past experience and/or knowledge on this case.

More important notes:
- All the content is still indexed, cant see changes there.
- I believe the meta tag did not pass w3c validation since I was supposed to
close the tag using /> like I do on that specific site.
- Taking snippets of the content from my index page does not show my site.
Only if I use quotation marks. And I noticed that it shows also domain.com AND domain.com/index.html (index.html is supplemental)
- I do use .htaccess for www/non-www issues. Though if some one goes to domain.com/index.html it remains as is.

Another thing I just noticed is - since the date that appears in google's cache,
logs show that they did not crawl the index page. only some inner pages.

New findings!

Google's webmaster tools now shows more clear information.
It seems some one was working hard in placing links to my site's inner pages which drug names anchors!
I see it on the "Top search queries" and in "In external links to your site"..

Also for some reason the encoding shows - US-ASCII as the most used and I use only UTF-8 on that site.

I would appreciate any replys.

The combination of being index page specific and the disappearance from allinanchor results would suggest a glitch to me...

Thank you for your comment Glengara. Tomorrow I will file a re-inclusion request
although as a site which is participating in affiliate programs, I do not know how
google will react, since as I recall reading some where that they clearly said
that sites gaining profits mostly from affiliate programs will have much explaining
to do. more than others.

I do believe that the site can improve, it always can. Especially in issues such as
usability. My content is by far better than my competitors and we even write
our own daily news.

All content is unique and while other sites gather unrelated links, I always
tried to avoid link schemes (Exchanged, purchased and so on..)

There is so much more that we do better than the others and in all terms I
think we are better. Which makes it even harder to understand.