I have got a website with almost 1000 pages; 800 where on Google's index in Oct 2010; today there are only 85!
From what I can recall doing in October:
a) I added code to redirect example.com to www.example.com
b) added a hotlink prevention script for resources
c) removed references to the default page (show.asp) in all URLs, because of the planned move to PHP (and the changing extension)
... and left the site alone; until I checked my Google stats today
This is what is desired:
1. any link to the site should be www.example.com/?topic=n
not showing www.example.com/show.asp?topic=n
2. I have a link rel=canonical www.example.com/?topic=n in the HTTP header for all pages
Google Webmaster Tools report under Crawl Errors:
www.example.com/?topic=123 redirect error unavailable
for both "sitemap" and "not followed"
Using FireBug to read the headers shows a HTTP 200 for all www.example.com/?topic=123 pages
.. and shows the 302 for any example.com/?topic=123 pages then directed to www.example.com/?topic=123
I am at the end of my wisdom, and do not understand why my pages have dropped off.
My aim with the canonical was to get rid of duplicate contents, which was recommended by the WebMasterTool; I feel in doing so, I killed my site, and subsequent AdSense $$.
Any hints would be much appreciated.