Supporters of the ATOM format also needs to add support for RSS so that those who only have RSS support can also see the content, which is still the great majority of people who subscribe to web feeds.

http://www.differencebetween.net/technology/difference-between-rss-and-atom/#ixzz1RTwQ79rt

从这里看到的，大家做 rss 的时候都是提供两个吗？还是只 atom feed 或者只 rss feed?