You need to edit the files item.php and category_item.php.

Below are three text blocks:

You replace the contents of the files item.php and category_item.php with the FIRST text block.

The following text blocks are snippets of code that are to be replaced in the above mentioned files.

Finally, after you replace text in category_item.php you will need to change:
<span class="itemExtraFieldsLabel"> to <span class="catItemExtraFieldsLabel"> and 
<span class="itemExtraFieldsValue"> to <span class="catItemExtraFieldsValue">

___________

<ul>
   <?php foreach ($this->item->extra_fields as $key=>$extraField):?>
      <?php if((!empty($extraField->value)) && (($extraField->value)!= "http://")) : ?>
         <?php $class = ($class == 'even')? 'odd' : 'even'; ?>
         <li class="<?php echo $class; ?> type<?php echo ucfirst($extraField->type); ?> group<?php echo $extraField->group; ?>"> <span class="itemExtraFieldsLabel"><?php echo $extraField->name; ?>:</span> <span class="itemExtraFieldsValue"><?php echo $extraField->value; ?></span> <br class="clr" />
         </li>
      <?php else : ?>
         <?php /*?>If for some reason you wanted something else to show in place of an empty field, you would put it here. You may need to wrap it in an li for proper formatting<?php */?>
      <?php endif; ?>
   <?php endforeach; ?>
</ul>

Original from item.php:
        <ul>
         <?php foreach ($this->item->extra_fields as $key=>$extraField):?>
         <li class="<?php echo ($key%2)? "odd" : "even"; ?> type<?php echo ucfirst($extraField->type); ?> group<?php echo $extraField->group; ?>">
            <span class="itemExtraFieldsLabel"><?php echo $extraField->name; ?>:</span>
            <span class="itemExtraFieldsValue"><?php echo $extraField->value; ?></span>
         </li>
         <?php endforeach; ?>
         </ul>

Original from category_item.php:
        <ul>
         <?php foreach ($this->item->extra_fields as $key=>$extraField): ?>
         <li class="<?php echo ($key%2)? "odd" : "even"; ?> type<?php echo ucfirst($extraField->type); ?> group<?php echo $extraField->group; ?>">
            <span class="catItemExtraFieldsLabel"><?php echo $extraField->name; ?></span>
            <span class="catItemExtraFieldsValue"><?php echo $extraField->value; ?></span>
         </li>
         <?php endforeach; ?>
         </ul>