And So I setted in the following lines to be able to redirect some demands to my static domain:

RewriteEngine On
RewriteBase /

RewriteRule ^img/(.*)$ http://static.mydomain.com/img/$1 [R=301] 
RewriteRule ^css/(.*)$ http://static.mydomain.com/css/$1 [R=301]
RewriteRule ^js/(.*)$ http://static.mydomain.com/js/$1 [R=301,L]

But for whatever reason, after i connect to a, let us say, an image:

<img src="img/icons/hello.png">

It's showing 404 if this really is available on static server (which really means it isn't being rerouted).

What shall we be held doing wrong? I spent like two hrs trying everything I understand but no fix found.

Thanks greatly ahead of time. Here's my full htaccess file:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /

    RewriteRule ^img/(.*)$ http://static.mydomain.com/img/$1 [R=301] 
    RewriteRule ^css/(.*)$ http://static.mydomain.com/css/$1 [R=301]
    RewriteRule ^js/(.*)$ http://static.mydomain.com/js/$1 [R=301,L]

    RewriteCond %{REQUEST_URI} ^system.*
    RewriteRule ^(.*)$ /index.php?/$1 [L]

    RewriteCond %{REQUEST_URI} ^application.*
    RewriteRule ^(.*)$ /index.php?/$1 [L]

    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php?/$1 [L]
</IfModule>

<IfModule !mod_rewrite.c>
    ErrorDocument 404 /index.php
</IfModule> 

One great way to debug the rewrites would be to specify RewriteLog and RewriteLogLevel. You place log gain levels to 9 which logs a great deal of reasons for the rewrites. Make sure to disable the logging after debugging, since it is quite heavy for that apache process.

RewriteLog documentation