Cannot add mod_headers in htaccess


I have htaccess file which is

I put the htaccess file on the root of my yii web project which contains mod_header.


But, when I tested in Yslow, it still gave me [color="#FF0000"]add expires header[/color] error (attached)

Does anyone know why Yii is like ‘ignoring’ the htaccess rule or just how to resolve errors that is given by Yslow?