How to customize a single default taxonomy page?
If you are using the standard issue taxonomy module to output your pages, eg:

www.yourhost.com/taxonomy/term/###  (or whatever its eventual alias is)


you can modify taxonomy-term.tpl.php to do almost anything you want.

In D7, it's provided for you and basically looks like this:

&lt;div id="taxonomy-term-&lt;?php print $term-&gt;tid; ?&gt;" class="&lt;?php print $classes; ?&gt;"&gt;

  &lt;?php if (!$page): ?&gt;
    &lt;h2&gt;&lt;a href="&lt;?php print $term_url; ?&gt;"&gt;&lt;?php print $term_name; ?&gt;&lt;/a&gt;&lt;/h2&gt;
  &lt;?php endif; ?&gt;

  &lt;div class="content"&gt;
    &lt;?php print render($content); ?&gt;
  &lt;/div&gt;

&lt;/div&gt;


The key variable to your question is $term and you could do something like this:

&lt;div id="taxonomy-term-&lt;?php print $term-&gt;tid; ?&gt;" class="&lt;?php print $classes; ?&gt;"&gt;

  &lt;?php if (!$page): ?&gt;
    &lt;h2&gt;&lt;a href="&lt;?php print $term_url; ?&gt;"&gt;&lt;?php print $term_name; ?&gt;&lt;/a&gt;&lt;/h2&gt;
  &lt;?php endif; ?&gt;

  &lt;div class="content"&gt;
    &lt;?php if ($term-&gt;tid==THE_TID_YOU_ARE_LOOKING_FOR): ?&gt;
       &lt;?php // do something different here ?&gt;
    &lt;?php else: ?&gt;
      &lt;?php print render($content); ?&gt;
    &lt;?php endif; ?&gt;
  &lt;/div&gt;

&lt;/div&gt;