location ~* ^.+\.(ico|gif|jpg|jpeg|png)$ {
    access_log off;
    expires 30d;
}

location ~* ^.+\.(css|js|txt|xml|swf|wav)$ {
    access_log off;
    expires 30d;
    add_header Cache-Control private;
}

location ~* ^.+\.(html|htm)$ {
    expires 1h;
}