Попробуйте добавить в htaccess:
# BEGIN Compress text files
AddOutputFilterByType DEFLATE text/html text/plain text/xml application/xml application/xhtml+xml text/css text/javascript application/javascript application/x-javascript
# END Compress text files
# BEGIN Expire headers
ExpiresActive On
ExpiresDefault "access plus 5 seconds"
ExpiresByType image/x-icon "access plus 2592000 seconds"
ExpiresByType image/jpeg "access plus 2592000 seconds"
ExpiresByType image/png "access plus 2592000 seconds"
ExpiresByType image/gif "access plus 2592000 seconds"
ExpiresByType application/x-shockwave-flash "access plus 2592000 seconds"
ExpiresByType text/css "access plus 604800 seconds"
ExpiresByType text/javascript "access plus 216000 seconds"
ExpiresByType application/javascript "access plus 216000 seconds"
ExpiresByType application/x-javascript "access plus 216000 seconds"
ExpiresByType text/html "access plus 600 seconds"
ExpiresByType application/xhtml+xml "access plus 600 seconds"
# END Expire headers
# BEGIN Cache-Control Headers
Header set Cache-Control "public"
Header set Cache-Control "public"
Header set Cache-Control "private"
Header set Cache-Control "private, must-revalidate"
Header append Vary: Accept-Encoding
Header set Cache-Control "max-age=43200"
Header set Cache-Control "max-age=604800"
Header set Cache-Control "max-age=2592000"
Header unset Cache-Control
# END Cache-Control Headers
# BEGIN Turn ETags Off
FileETag None
# END Turn ETags Off
