It's important not to be overly focused on the number of positions a keyword ranking dropped, especially when that number is very large. When your ranking falls from the top ten into a very deep position, it is often for "over optimization" or what people originally called "minus 950 [webmasterworld.com]".
Even when this penalty effect was first noticed, it wasn't always an exact "-950 penalty", and not even always "last page of results". It was often just a fall of several hundred positions. So I'd look into how your page might be over-optimized for these specific keywords, especially (but not only) through overuse of the keyword in anchor text.
The link I gave above summarizes the main ideas found in what is the longest running discussion we've had on the forum. That thread also has links to the very first thread on the topic (Jan 11, 2007) and the most recent, which is still live today (the last post was in May).
Thanks for your reply. I was wondering because I didn't set any link since 8 weeks - don't know if any other people set links of course. I even don't know it's a penalty (since the other keywords are doing fine), perhaps it's just a temporary flux in the updates google currently seems to do.
The page has been in the Top10 for a year now and it doesn't seem neccessary to do any excessive linkbuilding here. Thats why it seem so strange to me.
I can see exactly the same issue with one domain here in Germany. After some serious rotating of search results during the last days this domain has risen slightly for some competitive terms, but dropped for other terms to about position 30 to 100. Top20 to Top10 positions for these terms before the changes.
I am not sure if this is a kind of penalty: The domain still ranks very well, for some key even better than before and pages that lost rankings still rank for longtail searches. Only the results for some main keys dropped.
The site is not very heavy optimized on the onpage level. Additionally I havent gathered many links for this domain in the last months, so maybe it's just a normal shift in rankings: Other webmasters may have stronger links now or its because of too few links over a certain period of time...
Have seen this in the UK too - still ranking well for some medium level keywords but high value ones have dropped
I am hearing more and more reports of this happening in this newest wave of changes. Certainly some characteristics of the algorithm have changed considerably, or very new items are being added.
I see the same issue with some websites - where they rank perfectly fine for variations of keywords, and then are nowhere to be found for other variations.
I see some keywods coming back - a few of the ones which dropped not so far, more like Top10 - 80-90 - Top10.
I experienced the exact same occurrence to a few of my many keywords. It only appears that they were chosen at random to drop so dramatically, as their content have been pretty much the same for years. I've been given opinions ranging from tripping a duplicate content filter to over-optimization due to link building.
I'm just not sure since these problems have been steadily fixed for months, and our link building have been frugal to say the least.
Did anybody come back here yet?