Così dovrebbe andare

Codice PHP:
<?php

/************************************************************************/
/* PHP-NUKE: Advanced Content Management System                         */
/* ============================================                         */
/*                                                                      */
/* Copyright (c) 2002 by Francisco Burzi                                */
/* [url]http://phpnuke.org[/url]                                                   */
/*                                                                      */
/* This program is free software. You can redistribute it and/or modify */
/* it under the terms of the GNU General Public License as published by */
/* the Free Software Foundation; either version 2 of the License.       */
/************************************************************************/

if (stristr(htmlentities($_SERVER['PHP_SELF']), "header.php")) {
    Header("Location: index.php");
    die();
}

define('NUKE_HEADER', true);
require_once("mainfile.php");

##################################################
# Include some common header for HTML generation #
##################################################


function head() {
    global $slogan, $sitename, $banners, $nukeurl, $Version_Num, $artpage, $topic, $hlpfile, $user, $hr, $theme, $cookie, $bgcolor1, $bgcolor2, $bgcolor3, $bgcolor4, $textcolor1, $textcolor2, $forumpage, $adminpage, $userpage, $pagetitle;
    $ThemeSel = get_theme();
    include_once("themes/$ThemeSel/theme.php");
    echo "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\n";
    echo "<html>\n";
    echo "<head>\n";
    echo "<title>$sitename $pagetitle</title>\n";
    include("includes/meta.php");
    include("includes/javascript.php");
    if (file_exists("themes/$ThemeSel/images/favicon.ico")) {
    echo "<link rel=\"shortcut icon\" href=\"themes/$ThemeSel/images/favicon.ico\" type=\"image/x-icon\">\n";
    }
    echo "<link rel=\"alternate\" type=\"application/rss+xml\" title=\"rss\" href=\"backend.php\">\n";
    echo "<link rel=\"stylesheet\" href=\"themes/$ThemeSel/style/style.css\" type=\"text/css\">\n\n\n";
    echo "<!--[if IE ]>\n";
    echo "<link rel=\"stylesheet\" href=\"IE.css\" type=\"text/css\" />\n";
    echo "<![endif]-->\n";

    if (file_exists("includes/custom_files/custom_head.php")) {
      include_once("includes/custom_files/custom_head.php");
    }
    echo "\n\n\n</head>\n\n";
    if (file_exists("includes/custom_files/custom_header.php")) {
      include_once("includes/custom_files/custom_header.php");
    }
    themeheader();
}

online();
head();
include("includes/counter.php");
if(defined('HOME_FILE')) {
    message_box();
    blocks("Center");
}

?>
in pratica ho aggiunto questo:
Codice PHP:
    echo "<!--[if IE ]>\n";
    echo "<link rel=\"stylesheet\" href=\"IE.css\" type=\"text/css\" />\n";
    echo "<![endif]-->\n";