diff --git a/adm/admin.menu100.php b/adm/admin.menu100.php
index cc91af050..822c068fd 100644
--- a/adm/admin.menu100.php
+++ b/adm/admin.menu100.php
@@ -7,7 +7,7 @@ $menu['menu100'] = array (
     //array('100400', '버전정보', G5_ADMIN_URL.'/version.php', 'cf_version'),
     array('100800', '세션파일 일괄삭제',G5_ADMIN_URL.'/session_file_delete.php', 'cf_session', 1),
     array('100900', '캐시파일 일괄삭제',G5_ADMIN_URL.'/cache_file_delete.php',   'cf_cache', 1),
-    array('100910', '캡챠파일 일괄삭제',G5_ADMIN_URL.'/gcaptcha_file_delete.php',   'cf_captcha', 1),
+    array('100910', '캡챠파일 일괄삭제',G5_ADMIN_URL.'/captcha_file_delete.php',   'cf_captcha', 1),
     array('100920', '썸네일파일 일괄삭제',G5_ADMIN_URL.'/thumbnail_file_delete.php',   'cf_thumbnail', 1),
     array('100930', '네이버 신디케이션 핑',G5_SYNDI_URL.'/ping.php',   'cf_syndi_ping', 1),
     array('100500', 'phpinfo()',        G5_ADMIN_URL.'/phpinfo.php',       'cf_phpinfo'),
diff --git a/adm/gcaptcha_file_delete.php b/adm/captcha_file_delete.php
similarity index 92%
rename from adm/gcaptcha_file_delete.php
rename to adm/captcha_file_delete.php
index 1638d6dfb..b90fe3a03 100644
--- a/adm/gcaptcha_file_delete.php
+++ b/adm/captcha_file_delete.php
@@ -25,7 +25,7 @@ if (!$dir=@opendir(G5_DATA_PATH.'/cache')) {
 $cnt=0;
 echo '<ul>'.PHP_EOL;
 
-$files = glob(G5_DATA_PATH.'/cache/gcaptcha-*');
+$files = glob(G5_DATA_PATH.'/cache/?captcha-*');
 if (is_array($files)) {
     $before_time  = G5_SERVER_TIME - 3600; // 한시간전
     foreach ($files as $gcaptcha_file) {
diff --git a/css/default.css b/css/default.css
index fdfdce35e..87d9c48b1 100644
--- a/css/default.css
+++ b/css/default.css
@@ -195,8 +195,7 @@ a.btn_admin:focus, a.btn_admin:hover {text-decoration:none}
 fieldset .frm_input {padding:2px 2px 3px;border:1px solid #b8c9c2;background:#f7f7f7;color:#000;vertical-align:middle}
 
 /* 필수입력 */
-.required {background:url('../img/wrest.gif') #f7f7f7 top right no-repeat}
-textarea.required {background:url('../img/wrest.gif') #f7f7f7 top right no-repeat}
+.required, textarea.required {background:url('../img/wrest.gif') #f7f7f7 top right no-repeat}
 
 /* 테이블 항목별 정의 */
 .td_board {width:120px;text-align:center}
diff --git a/css/mobile.css b/css/mobile.css
index b6fdb010a..deed95377 100644
--- a/css/mobile.css
+++ b/css/mobile.css
@@ -159,8 +159,7 @@ a.btn_admin:focus, a.btn_admin:hover {text-decoration:none}
 .tbl_frm01 .frm_info {display:block;padding:0.3em 0 0;color:#666;line-height:1.3em}
 
 /* 필수입력 */
-.required {background:url('../img/wrest.gif') #f7f7f7 top right no-repeat}
-textarea.required {background:url('../img/wrest.gif') #f7f7f7 top right no-repeat}
+.required, textarea.required {background:url('../img/wrest.gif') #f7f7f7 top right no-repeat}
 
 /* 테이블 항목별 정의 */
 .td_board {width:120px;text-align:center}
diff --git a/install/gnuboard5.sql b/install/gnuboard5.sql
index 8b6cf0eda..8bcf3a82f 100644
--- a/install/gnuboard5.sql
+++ b/install/gnuboard5.sql
@@ -6,7 +6,7 @@
 
 DROP TABLE IF EXISTS `g5_auth`;
 CREATE TABLE IF NOT EXISTS `g5_auth` (
-  `mb_id` varchar(255) NOT NULL default '',
+  `mb_id` varchar(20) NOT NULL default '',
   `au_menu` varchar(20) NOT NULL default '',
   `au_auth` set('r','w','d') NOT NULL default '',
   PRIMARY KEY  (`mb_id`,`au_menu`)
@@ -281,7 +281,7 @@ CREATE TABLE IF NOT EXISTS `g5_config` (
   `cf_mobile_search_skin` varchar(255) NOT NULL DEFAULT '',
   `cf_mobile_connect_skin` varchar(255) NOT NULL DEFAULT '',
   `cf_mobile_member_skin` varchar(255) NOT NULL DEFAULT '',
-  `cf_gcaptcha_mp3` varchar(255) NOT NULL DEFAULT '',
+  `cf_captcha_mp3` varchar(255) NOT NULL DEFAULT '',
   `cf_editor` varchar(255) NOT NULL DEFAULT '',
   `cf_cert_use` tinyint(4) NOT NULL DEFAULT '0',
   `cf_cert_ipin` varchar(255) NOT NULL DEFAULT '',
@@ -325,7 +325,7 @@ CREATE TABLE IF NOT EXISTS `g5_config` (
 
 CREATE TABLE IF NOT EXISTS `g5_cert_history` (
   `cr_id` int(11) NOT NULL auto_increment,
-  `mb_id` varchar(255) NOT NULL DEFAULT '',
+  `mb_id` varchar(20) NOT NULL DEFAULT '',
   `cr_company` varchar(255) NOT NULL DEFAULT '',
   `cr_method` varchar(255) NOT NULL DEFAULT '',
   `cr_ip` varchar(255) NOT NULL DEFAULT '',
@@ -383,7 +383,7 @@ DROP TABLE IF EXISTS `g5_group_member`;
 CREATE TABLE IF NOT EXISTS `g5_group_member` (
   `gm_id` int(11) NOT NULL auto_increment,
   `gr_id` varchar(255) NOT NULL default '',
-  `mb_id` varchar(255) NOT NULL default '',
+  `mb_id` varchar(20) NOT NULL default '',
   `gm_datetime` datetime NOT NULL default '0000-00-00 00:00:00',
   PRIMARY KEY  (`gm_id`),
   KEY `gr_id` (`gr_id`),
@@ -399,7 +399,7 @@ CREATE TABLE IF NOT EXISTS `g5_group_member` (
 DROP TABLE IF EXISTS `g5_login`;
 CREATE TABLE IF NOT EXISTS `g5_login` (
   `lo_ip` varchar(255) NOT NULL default '',
-  `mb_id` varchar(255) NOT NULL default '',
+  `mb_id` varchar(20) NOT NULL default '',
   `lo_datetime` datetime NOT NULL default '0000-00-00 00:00:00',
   `lo_location` text NOT NULL,
   `lo_url` text NOT NULL,
@@ -432,7 +432,7 @@ CREATE TABLE IF NOT EXISTS `g5_mail` (
 DROP TABLE IF EXISTS `g5_member`;
 CREATE TABLE IF NOT EXISTS `g5_member` (
   `mb_no` int(11) NOT NULL auto_increment,
-  `mb_id` varchar(255) NOT NULL default '',
+  `mb_id` varchar(20) NOT NULL default '',
   `mb_password` varchar(255) NOT NULL default '',
   `mb_name` varchar(255) NOT NULL default '',
   `mb_nick` varchar(255) NOT NULL default '',
@@ -496,8 +496,8 @@ CREATE TABLE IF NOT EXISTS `g5_member` (
 DROP TABLE IF EXISTS `g5_memo`;
 CREATE TABLE IF NOT EXISTS `g5_memo` (
   `me_id` int(11) NOT NULL default '0',
-  `me_recv_mb_id` varchar(255) NOT NULL default '',
-  `me_send_mb_id` varchar(255) NOT NULL default '',
+  `me_recv_mb_id` varchar(20) NOT NULL default '',
+  `me_send_mb_id` varchar(20) NOT NULL default '',
   `me_send_datetime` datetime NOT NULL default '0000-00-00 00:00:00',
   `me_read_datetime` datetime NOT NULL default '0000-00-00 00:00:00',
   `me_memo` text NOT NULL,
@@ -576,7 +576,7 @@ DROP TABLE IF EXISTS `g5_poll_etc`;
 CREATE TABLE IF NOT EXISTS `g5_poll_etc` (
   `pc_id` int(11) NOT NULL default '0',
   `po_id` int(11) NOT NULL default '0',
-  `mb_id` varchar(255) NOT NULL default '',
+  `mb_id` varchar(20) NOT NULL default '',
   `pc_name` varchar(255) NOT NULL default '',
   `pc_idea` varchar(255) NOT NULL default '',
   `pc_datetime` datetime NOT NULL default '0000-00-00 00:00:00',
@@ -608,7 +608,7 @@ CREATE TABLE IF NOT EXISTS `g5_popular` (
 DROP TABLE IF EXISTS `g5_scrap`;
 CREATE TABLE IF NOT EXISTS `g5_scrap` (
   `ms_id` int(11) NOT NULL auto_increment,
-  `mb_id` varchar(255) NOT NULL default '',
+  `mb_id` varchar(20) NOT NULL default '',
   `bo_table` varchar(20) NOT NULL default '',
   `wr_id` varchar(15) NOT NULL default '',
   `ms_datetime` datetime NOT NULL default '0000-00-00 00:00:00',
diff --git a/install/install_db.php b/install/install_db.php
index 6af082fc4..bb2b77089 100644
--- a/install/install_db.php
+++ b/install/install_db.php
@@ -125,7 +125,7 @@ if($g5_install || !$result) {
                     cf_mobile_search_skin = 'basic',
                     cf_mobile_connect_skin = 'basic',
                     cf_mobile_member_skin = 'basic',
-                    cf_gcaptcha_mp3 = 'basic',
+                    cf_captcha_mp3 = 'basic',
                     cf_register_level = '2',
                     cf_register_point = '1000',
                     cf_icon_level = '2',
diff --git a/mobile/skin/member/basic/style.css b/mobile/skin/member/basic/style.css
index 79d435718..beb492d69 100644
--- a/mobile/skin/member/basic/style.css
+++ b/mobile/skin/member/basic/style.css
@@ -56,8 +56,7 @@
 */
 .mbskin .tbl_frm01 a {}
 
-.mbskin .required {} /* 필수입력 */
-.mbskin textarea.required {}
+.mbskin .required, .mbskin textarea.required {background:url('../../../../img/wrest.gif') #f7f7f7 top right no-repeat} /* 필수입력 */
 
 /* 테이블 항목별 정의 */
 .mbskin .td_board {}
diff --git a/plugin/kcaptcha/kcaptcha_mp3.php b/plugin/kcaptcha/kcaptcha_mp3.php
index d7c0cd35a..415ba48fc 100644
--- a/plugin/kcaptcha/kcaptcha_mp3.php
+++ b/plugin/kcaptcha/kcaptcha_mp3.php
@@ -3,7 +3,7 @@ include_once("_common.php");
 
 function make_mp3()
 {
-    global $g4, $config;
+    global $config;
 
     $number = get_session("ss_captcha_key");
 
@@ -26,10 +26,10 @@ function make_mp3()
 
     file_put_contents(G5_PATH.'/'.$mp3_file, $contents);
 
-    // 지난 캡챠 파일 삭제
-    if (rand(0,10) == 0) {
+    // 지난 캡챠 파일 삭제 (100번중에 한번만 실행)
+    if (rand(0,99) == 0) {
         foreach (glob(G5_PATH.'/data/cache/kcaptcha-*.mp3') as $file) {
-            if (filemtime($file) + 86400 < $g4['server_time']) {
+            if (filemtime($file) + 86400 < G5_SERVER_TIME) {
                 unset($file);
             }
         }
diff --git a/skin/member/basic/register_form.skin.php b/skin/member/basic/register_form.skin.php
index 52b6c380f..842145b72 100644
--- a/skin/member/basic/register_form.skin.php
+++ b/skin/member/basic/register_form.skin.php
@@ -5,7 +5,7 @@ if (!defined('_GNUBOARD_')) exit; // 개별 페이지 접근 불가
 <!-- 회원정보 입력/수정 시작 { -->
 <link rel="stylesheet" href="<?php echo $member_skin_url ?>/style.css">
 
-<div class="mb_skin">
+<div class="mbskin">
 
     <script src="<?php echo G5_JS_URL ?>/jquery.register_form.js"></script>
     <?php if($config['cf_cert_use'] && ($config['cf_cert_ipin'] || $config['cf_cert_hp'])) { ?>
diff --git a/skin/member/basic/style.css b/skin/member/basic/style.css
index bd28c3ed3..405d1fdda 100644
--- a/skin/member/basic/style.css
+++ b/skin/member/basic/style.css
@@ -44,26 +44,25 @@
 .mbskin td.empty_table {}
 
 /* 폼 테이블 */
-.mb_skin table {}
-.mb_skin caption {}
-.mb_skin .frm_info {}
-.mb_skin .frm_address {}
-.mb_skin .frm_file {}
+.mbskin table {}
+.mbskin caption {}
+.mbskin .frm_info {}
+.mbskin .frm_address {}
+.mbskin .frm_file {}
 
-.mb_skin .tbl_frm01 {}
-.mb_skin .tbl_frm01 th {}
-.mb_skin .tbl_frm01 td {}
-.mb_skin .tbl_frm01 textarea, .mb_skin tbl_frm01 .frm_input {}
-.mb_skin .tbl_frm01 textarea {}
+.mbskin .tbl_frm01 {}
+.mbskin .tbl_frm01 th {}
+.mbskin .tbl_frm01 td {}
+.mbskin .tbl_frm01 textarea, .mb_skin tbl_frm01 .frm_input {}
+.mbskin .tbl_frm01 textarea {}
 /*
-.mb_skin .tbl_frm01 #captcha {}
-.mb_skin .tbl_frm01 #captcha input {}
+.mbskin .tbl_frm01 #captcha {}
+.mbskin .tbl_frm01 #captcha input {}
 */
-.mb_skin .tbl_frm01 a {}
+.mbskin .tbl_frm01 a {}
 
 /* 필수입력 */
-.mbskin .required {}
-.mbskin textarea.required {}
+.mbskin .required, .mbskin textarea.required {background:url('../../../img/wrest.gif') #f7f7f7 top right no-repeat}
 
 /* 테이블 항목별 정의 */
 .mbskin .td_board {}