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Url A -> dropped
Url B with 301 to Url A.
Url B ist very old and Supplemental in the index, but the Googlebot still visit this Url regularly. (First Url B, then Url A)
I still have 20% of my pages in the index and the Bot visit these regularly. The most of these pages have no old URL with 301.
I have changed my URL system in October 2005. I have put the 301 redirects on 7th april 2006, before I send 410. After this, the dropping began. Can it be that Google does not cope with that? Should I better send 410, instead of 301?
However, there also are a few counterexamples (Pages dropped out without 301, Pages in with 301).
You could use Google's URL removal tool to remove your old URLS provided there is no page there, and it must show a 404 Page Not found.
Are you sure you are not accidentally doing a 302 instead? This is a common error. That would be DEADLY.
We had some redirects that we could have SWORN were 301s, but we discovered to our horror they were 302 redirects.
On some servers if you do not specify explicitly in the command line that you want a 301 redirect, your server gives you a 302 redirect. OOPS!
How do you test for sure? I like to use Seoconsultants server headers tool. To find it just search this in google with quotes:
"Check Server Headers Tool - HTTP Status Codes Checker"
All you do is enter the URL that you are redirecting into their header tool form online, and look at the output of the form, for the line that says "HTTP Status Code", and see if it says 301 or 302. If it says 302, then you have work to do.
Moral of the story, DO NOT ASSUME you have a 301 redirect unless it is explicitly called out in your command line.
I have always been a fan of abo#*$!e addressing over relative addressing for reasons like this. Never take chances.