Have you tested by simply putting {$smarty.get.page} and seeing what the results are? I believe that variable shows the result of _get requests.
Try {$smarty.server.REQUEST_URI}:
PHP Code:
{if strpos($smarty.server.REQUEST_URI, "SWCHS.html") !== false}
<p>SWCHS image/CSS</p>
{else}
default image/css
{/if}