Problem for browser cache

Hi everyone,

I have a little problem with the plugin "Hummingbird".
When I try to change the browser cache duration for "css" and "javascript" is blocked to 15minutes...

I've tried to paste the generate code into my .htaccess files but it doesn't work too :slight_frown:.

I join a screenshot to show you my problem.

Excuse me for my English, I'm a little French :smiley: