this is not common but has happened in the past. historically this sometimes was caused when people were hitting different google data centers that were not in sync or were being used for testing new algos. there are other less common reasons this historically could have happened.
as for your current situation i am a little curious about a few things:
-are you always logged into the same google account when you search?
-are you using the same computer & ip?
-how are you searching the google index to see if your content is included or excluded?
-is this content 100% unique with no duplication on any other website?
- I'm always logged in the same account and am using Firefox. When I suspect that something might be biased, I switch to IE or Safari (without logging in)
- same computer and IP
- when I want to check whether an article has been included, I usually search for its title or simple copy a chunk of the url address and wrap with quotes.
- its 100% unique content
I have checked with some colleagues who live in different cities, results are somewhat mixed. But today it seems it vanished from all searches.
Still, I see some people arriving via google for the mentioned articles.
For example - I see people arriving via "http://www.google.com/search?q=title%20of%20my%20article", but when I try the same search my article is nowhere to be found.
It sounds like your new articles are getting into the "minty fresh" index when you first publish them. Pages in "minty fresh" only last a few days, so once they expire they seem to "disappear" until they're included in the main index. Blogs and news sites see this quite a lot.
lately more and more websites are noticing this. it tends to impact websites using a blog cms. i would suggest you work on improving your external & internal link popularity. it will help but not solve the situation.
also you should double check that someone is not scraping your rss feed and creating duplicate content issues after the fact. i doubt that is the case but it is simple to check.
Luckily I haven't noticed any scraping of my content yet, but I do check occasionally.
As rainborick mentioned - the content is indeed inexed as "minty fresh" and will occupy top positions as soon as it is published.
Usually these drop down a place or two after Google saves it into "cache".
But for my latest articles, they disappeared completely and are not coming back (4th day now).
Its as if Google perceives it as some "breaking news", keeps it around for a couple of hours and then drops it out.
Btw, this is not a blog. I coded the entire page from scratch, including my own cms system etc.
I'm confident my code is good and very well seo optimized.
A lot things going on right now , I saw too crazy and wild dancing on index for my own websites .
There are SE changes with Instant Previews + new algo + upcoming features , so we must wait to everything settle down ... eventually.
macas, you are correct.
Let me confirm that today my results are back in normal (4 days later).
The latest articles that had vanished from index have returned and rank as they should.
I too believe it had something to do with Google's new features. Mainly because the day I realized my articles were dropped was the day I spotted that little magnifying glass.
We talk about Google's dance a lot, but I'm still puzzled as to why this has to happens when Google makes certain improvements?
Google should pay more attention to the stability of their ranks.
In the case of web previews, it's not just a new feature in the user interface. It comes along with new infrastructure - specifically the new Web Preview bot. See [webmasterworld.com...]
Now the instability of recent days is a little more easily understood. Not forgiven, mind you - just understood ;)
As long as these naughty situations resolve themselves in a matter of days, we are content :)