Why sometimes the site of the forum signature does not show?
 

Who can help me solve the problem, give me some good suggestions, Thank you very much.I found a lot of other friends signature does not show. Why is that?

In some forums which are especially high PR and do follow, you will not see your signature below your post because for that you will have to reach a certain number of posts in the forum according to their rules and regulation and after that they will allow you to put the signature in the forum. They are doing this to avoid the spammer in the site.

Sometimes you can only see the signature while in logged in mode. e.g is DP forums.