at the moment wp-syntax does this to add its stlye:
$css_url = WP_PLUGIN_URL . "/wp-syntax/wp-syntax.css";
echo "\n".'<link rel="stylesheet" href="' . $css_url . '" type="text/css" media="screen" />'."\n";
It would be better to use the wordpress standard way to include plugins
wp_enqueue_style("WP-Syntax", WP_PLUGIN_URL . "/wp-syntax/wp-syntax.css", false, false, "screen");
by doing so the css can be modified by other plugins, or which is important for me, can be combined by mod_pagespeed, as this causes the css file to appear next to each other.