Re Twitter. If I reply to a tweet, do my followers see my reply?

[Heidi]

When your message begins with @username, it doesn't go on your followers' homepages unless they are also following that person. For example, I have some followers who also follow @shakira. So if I typed "@Shakira I love your new video!" then some of my followers would see it on their homepages.

If you put @username in the middle or end of your post, it goes on all of your follower's homepages. So if I typed "I love @Shakira's new video!" all of my followers would see it.

However, keep in mind that anytime someone clicks on your profile, they see ALL of your tweets including @replies. If you want something kept private, use the Direct Message feature.