What type of text should it be?
One possibility would be
create a new position (group) in the template
and after that create an new field (filedtype = text area) also
so you can, when editing a category,
write a text for each category that appears under the table
I do not know whether you mean it.
To implement this you must do the following changes:
1. add a new group (e.g. under_tabe) in the templates\default\category.xml
Code:
<fieldgroups>
<group>table</group>
<group>under_table</group>
</fieldgroups>
2. in the templates\default\category.php
after
Code:
<!-- BOF item list display -->
<?php echo $this->loadTemplate('items'); ?>
<!-- BOF item list display -->
add the following code
Code:
<?php if ((isset($this->item->positions['under_table'])) : ?>
<div class="under_item_table">
<!-- BOF under_item_table block -->
<?php foreach ($this->item->positions['under_table'] as $field) : ?>
<div class="element <?php echo $field->name; ?>">
<?php echo $field->display; ?>
</div>
<?php endforeach; ?>
</div>
<div class="clear"></div>
<?php endif; ?>
<!-- EOF under_item_table block -->
the code for the css file and the rest of the statement I skip
maybe that is right for you