When a page on your site totally tanks in Google's search results, normally there is one of several things that have gone wrong to have caused it.
- You have messed up – maybe blocked the page by accident in robots.txt
- Google have made a major algorithm change
- You have some kind of general penalty or your site has been hacked
It could also be argued that it can be caused by duplicate content, and enter the supplemental results through lack of pagerank. Honest duplicate content could be on your own site, or due to poor syndication (lack of links back to the original document).
There
