OK! Some rss readers are more strict regarding the formatting. Well, but it seems that I got it fixed, as Firefox isn't complaining anymore.

Yup, I think tags would be helpful for newcomers, who might be interested in reading some of the older posts but find it clumsy to browse back the title list. Like, some of the older posts are steadily accumulating "likes", so maybe I have to believe that there are real people reading out there =)