Possible Duplicate:
Why the # of indexed pages got dicreased?
My site's indexed pages drop every now and then. It suddenly drops from ~800.000 to ~20.000 pages, along with a huge drop in daily crawled pages (according to Google's webmaster tools) Then it raises again during the next 1-2 months, just to drop again, and the cycle repeats.
I happens in both site:www.example.com and example.com. I'm very worried and I can't figure out why is this happening without making any changes in the site's link structure.
This is affecting our rankings too. I suspect there's something annoying Goggle in our site, but it's driving me nuts to find the clue.
robots.txt
file?