How can i preview a form value before submit?

[colap]

How can i preview a form value before submit?

<form method="POST" action="p.php">
<table>
  <tr><td>Username</td><td><input type="text" name="username" id="id_username" /></td></tr>
  <tr><td>Fathers name</td><td><input type="text" name="f_username" id="id_f_username" /></td></tr>
  <tr><td><input type="submit" value="Submit" /></td></tr>
</table>
</form>

It will be like "Preview Post" of phpfreaks forum.

[requinix]

All you have in that form is two textboxes. Are you really sure you need a preview for them?

 

Whatever. Use two buttons in the form: one to submit normally, one to go to a preview mode. If the user clicks the preview mode button then you don't process the form like you would have but instead show the form information in some "preview" form or another.