lucy24 - 12:17 am on Nov 9, 2012 (gmt 0)
I am at the same position -
^184.108.40.206 = no alternative image
!^220.127.116.11 = always alternative image
Whenever you say . quoting your htaccess you really mean \.
Whenever you say ^18.104.22.168 you really mean your own IP
:: grasping at straws ::
Any difference if you also give a $ closing tag for the IP?
What do your logs say? A rewrite will come through as 200, but the filesize will be different-- assuming the alternative file is a different size. For testing it can be useful to use a redirect instead of a rewrite, because then you can see it clearly in your logs.