I'm totally new to caching so sorry if I'm missing something obvious but I've been struggling with this for hours.
Firebug has been telling me to "Leverage browser caching". So I installed W3 Total Cache. I've enabled browser cache (although it wasn't selected by default) and I've turned on all the options within it that section and deployed it.
Firebug is still giving me the same warning for my .css .jpg and .js files.
I've made a text copy of the .htaccess file for you to take a look at here (that's also the site which is having the problem).
Check compatibility is showing some problems:
PHP Timezone: Not set
Opcode cache: Not installed
Memcache extension: Not installed
mod_mime: Not detected
mod_expires: Not detected
mod_deflate / mod_gzip: Not detected
mod_headers: Not detected
mod_env: Not detected
I'm not really sure what these mean but I've read W3TC sometimes has a problem detecting these things when they are actually there.
I'd appreciate any help I can get on this.