diff --git a/head.php b/head.php
index a9a14d967..d574bd650 100644
--- a/head.php
+++ b/head.php
@@ -114,9 +114,11 @@ if (G5_IS_MOBILE) {
             <?php
             $sql = " select * from {$g5['group_table']} where gr_show_menu = '1' and gr_device <> 'mobile' order by gr_order ";
             $result = sql_query($sql);
+            $gnb_zindex = 999; // gnb_1dli z-index 값 설정용
             for ($gi=0; $row=sql_fetch_array($result); $gi++) { // gi 는 group index
+                $gnb_zindex -= 1; // html 구조에서 앞선 gnb_1dli 에 더 높은 z-index 값 부여
              ?>
-            <li class="gnb_1dli">
+            <li class="gnb_1dli" style="z-index:<?php echo $gnb_zindex; ?>">
                 <a href="<?php echo G5_BBS_URL ?>/group.php?gr_id=<?php echo $row['gr_id'] ?>" class="gnb_1da"><?php echo $row['gr_subject'] ?></a>
                 <ul class="gnb_2dul">
                     <?php
diff --git a/install/index.php b/install/index.php
index 273d6716c..056b399c0 100644
--- a/install/index.php
+++ b/install/index.php
@@ -1,12 +1,13 @@
 <?php
 include_once ('../config.php');
 $title = G5_VERSION." 라이센스 확인 1/3";
-require_once('./library.check.php');
 include_once ('./install.inc.php');
 ?>
 
 <?php
 if ($exists_data_dir && $write_data_dir) {
+    // 필수 모듈 체크
+    require_once('./library.check.php');
 ?>
 <form action="./install_config.php" method="post" onsubmit="return frm_submit(this);">
 
diff --git a/install/library.check.php b/install/library.check.php
index 08889cc50..c01d9643e 100644
--- a/install/library.check.php
+++ b/install/library.check.php
@@ -1,14 +1,9 @@
 <?php
 if (!defined('_GNUBOARD_')) exit; // 개별 페이지 접근 불가
 
-function die_utf8($msg)
-{
-    if(!trim($msg))
-        return;
-
-    die('<meta charset="utf-8"><p>'.$msg.'</p>');
+if(!extension_loaded('gd') || !function_exists('gd_info')) {
+    echo '<script>'.PHP_EOL;
+    echo 'alert("'.G5_VERSION.'의 정상적인 사용을 위해서는 GD 라이브러리가 필요합니다.\nGD 라이브러리가 없을 경우 자동등록방지 문자와 썸네일 기능이 작동하지 않습니다.");'.PHP_EOL;
+    echo '</script>'.PHP_EOL;
 }
-
-if(!extension_loaded('gd') || !function_exists('gd_info'))
-    die('GD 라이브러리를 설치하신 후 '.G5_VERSION.' 설치를 진행해 주십시오.');
 ?>
\ No newline at end of file
diff --git a/lib/common.lib.php b/lib/common.lib.php
index de725408f..e36816502 100644
--- a/lib/common.lib.php
+++ b/lib/common.lib.php
@@ -1883,10 +1883,7 @@ function convert_charset($from_charset, $to_charset, $str)
 function escape_trim($field)
 {
     if ($field) {
-        $str = mysql_real_escape_string(@trim($field));
-
-        //if(PHP_VERSION < '5.3.0')
-        //    $str = stripslashes($str);
+        $str = call_user_func(G5_ESCAPE_FUNCTION, $field);
 
         return $str;
     }