Dynamic code for DL link icons

Apologies for the poorly worded title/summary for this one!

The code that is used to create the DL links on a web page needs to be amended to dynamically detect and use the file type of the document being offered for download.

This works for text and pdf files because these were originally hard-coded a few years ago. However, word documents, pps, xls and so on are NOT considered. They all simply get called 'file-url':

e.g.

<div class="urls">
          <span class="field">Download:</span>
          <span class="value">
            <a class="file-url"
               href="URL/uob-isd.pps">pps</a>
            <a class="pdf-url"
               href="URL/uob-isd.pdf">pdf</a>
          </span>
</div>

NB: Actual URL replaced with 'URL' in the above example!

In the above it knows the file is a 'pps' so can it not simply dynamically create <a class="pps-url" rather than use <a class="file-url" so the style sheet can include an icon for pps, etc?

(We had some custom code written by David, amending the renderer.py and then adding new styles into the CSS. This obviously isn't in the DL now sitting on the test server and we noticed some document icons were missing!)