drupal block

Template files are searched in the following order:

•      block-[module]-[delta].tpl.php
•      block-[module].tpl.php
•      block-[region].tpl.php
•      block.tpl.php

For example, the user login block has a delta of '0'. If you put it in the left sidebar, when it's rendered, PHPTemplate will search for the following templates in descending order:

•      block-user-0.tpl.php
•      block-user.tpl.php
•      block-left.tpl.php
•      block.tpl.php

You can find the block's module and delta by looking at the html source of a page: each block's main DIV has the following classes and IDs:

  
<div class="block block-<?php print $block->module; ?>" 
id="block-<?php print $block->module; ?>-
<?php print $block->delta; ?>">
    <h2 class="title"><?php print $block->subject; ?></h2>
    <div class="content"><?php print $block->content; ?></div>
 </div>