Meaning that if you put your image file outside the document root like below
docroot/ -- assets/ -- img/ -- apple-touch-icon-precomposed.png
You need to redirect them using mod_rewrite to the actual path. In you .htaccess, add these lines.
RewriteEngine On RewriteRule ^apple-touch-icon-precomposed\.png$ assets/img/apple-touch-icon-precomposed.png [L]
When I checked my .htaccess file, I noticed I did the same for favicon.ico as well and it never cross my mind to do the same for this !