If you have a design element in your site that you only want to show to registered customers, and hide from retail customers, then you need place the following tags
before the code:
<Actinic:NOTINB2B><!--</Actinic:NOTINB2B>
…and put these after the code:
<Actinic:NOTINB2B>--></Actinic:NOTINB2B>
You also need to ensure that you are not compacting HTML otherwise they will be stripped out when uploaded ('Design | Options | Miscellaneous' for v7 and earlier or 'Design | Design Options' for v8 and higher).
This will mean that the HTML comment marks will only appear for unregistered customers, and hence the content will be hidden from them.