From Facebook Developers Wiki

[edit] Description

Renders a wall-style post. You should use it inside fb:wall tags, but it renders fine without them. It can also contain an fb:wallpost-action tag, which places a link at the bottom of the post.

[edit] Attributes

Required	Name	Type	Description
required	uid	int	The user ID of the author of the post. FBML cannot parse without it, resulting in a runtime error. If the user ID is invalid (for example, the account has been deleted) then an image of a question mark and no name appear.
optional	t	int	The current time, which is displayed in epoch seconds. (Default value is empty, no time/date is displayed with the wall post.)

[edit] Examples

<fb:wallpost uid="10" t="1180502413"> This tag exists outside <fb:wall> tags. <br /> It has the t attribute set to 1180502413 </fb:wallpost> <fb:wall> <fb:wallpost uid="11"> This tag exists inside <fb:wall> tags. It has no t attribute set </fb:wallpost> </fb:wall>