i created a BusinessPartner DataObject
here is the structure

root
businesspartner/
.. _config.php
.. code/
....BusinessPartner (extends DataObject)
....BusinessPartnerAdmin (extends ModelAdmin)
mysite
sapphire
..
..
..

=====================
in my page i added

// class Page extends SiteTree
...
...
public static $db = array('BusinessPartner' => 'Boolean');

function getCMSFields() {
    $fields->addFieldToTab("Root.Content.BusinessPartner", new CheckboxField('BusinessPartner', 'Include a Business Partner on this page?'));
}
...
...

function BusinessPartner() {
  if($this->BusinessPartner) {
    $d['BusinessPartner'] = DataObject::get('BusinessPartner');
      return $this->customise($d)->renderWith('BusinessPartner');
  }
  return FALSE;
}

=====================

in templates/Layout/Page.ss
i add $BusinessPartner (after $Content)

i also create a Layout for BusinessPartner (templates/Layout/BusinessPartner.ss)

when the page created, the data showed. but the HTML tag not showed correctly. instead its showed all html tags

<table border="1">
<tr>
<td>Agent Name</td>
<td>Address</td>
<td>Tel / Fax</td>
<td>PIC</td>
<td>Email</td>
</tr> 
<% control BusinessPartner %>
<tr>
	<td>$AgentName</td>
	<td>$Address</td>
	<td>$Telephone / $Fax</td>
	<td>$PicAgent</td>
	<td><a href="mailto:$Email">$Email</a></td>
</tr>
<% end_control %>

the tag <table>, <tr>, <td> showed, and the data from control BusinessPartner looped from database.

what i missed here ???

There is no closing </table> tag, that could be it.