Passing a filename to the firefox browser causes it to replace spaces with
<img src="C:\Documents and Settings\screenshots\Image01.png"/>
^-----Firefox changed my space to %2520.
A bit of explaining as to what that
%2520 is :
The common space character is encoded as
%20 as you noted yourself.
% character is encoded as
The way you get
%2520 is when your url already has a
%20 in it, and gets urlencoded again, which transforms the
Are you (or any framework you might be using) double encoding characters?