nginx add for rails 3.1 and above with paperclip support

gistfile1.txt

location ~* ^/(assets|images|javascripts|system)/ {
	# Per RFC2616 - 1 year maximum expiry
    # http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
    expires 1y;
    add_header Cache-Control public;

    # Some browsers still send conditional-GET requests if there's a
    # Last-Modified header or an ETag header even if they haven't
    # reached the expiry date sent in the Expires header.
    # Do NOT unset Last-Modified!
    # add_header Last-Modified "";
    add_header ETag "";
    break;
}