My setup matches w3mmode [[w3mmode/ikiwiki.setup]] exactly.  
My doc/index.mdwn just has a line or two of plain text.  
When I try to edit that page in w3m, it works fine until I push [Save Page].  
Then I just get a page that only contains "403".

ikiwiki version is 3.20110715ubuntu1.  
w3m is 0.5.3.

-- [[terry|tjgolubi]]
