[Jon]

I've experimented with different configurations but this principle has proved the most effective:

Open smarty.php

FIND:

$smarty->assign("SkinDir",$xcart_web_dir."/skin1");
$smarty->assign("ImagesDir",$xcart_web_dir."/skin1/images");

REPLACE WITH:

// WCM - MaxCDN Implementation
if ($_SERVER['HTTPS'] != 'on')
{
     $smarty->assign("SkinDir","http://CdnUrl.example.com/skin1");
     $smarty->assign("ImagesDir","http://CdnUrl.example.com/skin1/images");
}
else
{
     $smarty->assign("SkinDir",$xcart_web_dir."/skin1");
     $smarty->assign("ImagesDir",$xcart_web_dir."/skin1/images");
}
// WCM - MaxCDN Implementation