404 11 0 error in log files

[speedshopping]

We have a .net site that rewrites it's urls from .aspx to friendly urls. Whilst looking through our log files we have noticed that googlebot is sometimes returning a 200 0 0 response by crawling the .aspx raw URL as it should, but other times the bot tries to crawl the rewritten friendly URL and returns a 404 11 0... Can anyone shed any light on why this is happening and how to fix this issue - we believe it's the cause of major traffic loss which happened after the 29th dec.

Thanks for your help!

[Ocean10000]

The error is that the url was double escaped. And by default II7 doesn't allow that to be processed. See the following KP article for more details.

HTTP Error 404.11 – URL_DOUBLE_ESCAPED [support.microsoft.com]