diff --git a/content/treestyletab/treestyletab-3.1.css b/content/treestyletab/treestyletab-3.1.css
index c7ae056a..3257e831 100644
--- a/content/treestyletab/treestyletab-3.1.css
+++ b/content/treestyletab/treestyletab-3.1.css
@@ -1,6 +1,10 @@
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 @namespace html url("http://www.w3.org/1999/xhtml");
 
+tabbrowser[treestyletab-hide-newtab-button="true"] .tabs-newtab-button {
+	visibility: collapse !important;
+}
+
 tabbrowser .tabs-container > .tabbrowser-arrowscrollbox {
 	-moz-binding: url("chrome://treestyletab/content/treestyletab.xml#tabbrowser-arrowscrollbox");
 }
diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index d6c2bf0a..57bf3c20 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -28,7 +28,6 @@ tabbrowser[treestyletab-tabbar-fixed="true"] .tabbrowser-strip+splitter {
 tabbrowser:not([treestyletab-mode="horizontal"]) .tabbrowser-arrowscrollbox > .scrollbutton-up,
 tabbrowser:not([treestyletab-mode="horizontal"]) .tabbrowser-arrowscrollbox > .scrollbutton-down-stack,
 tabbrowser:not([treestyletab-mode="horizontal"]) .tabbrowser-arrowscrollbox > .scrollbutton-down, /* Firefox 3 */
-tabbrowser[treestyletab-hide-newtab-button="true"] .tabs-newtab-button, /* "open a new tab" button in Firefox 3.1 */
 tabbrowser[treestyletab-hide-alltabs-button="true"] .tabs-alltabs-stack,
 tabbrowser[treestyletab-hide-alltabs-button="true"] .tabbrowser-arrowscrollbox ~ stack, /* "all tabs" button in Firefox 3 and 3.1 */
 tabbrowser[treestyletab-mode="vertical"] .tabs-closebutton-box,
@@ -39,10 +38,6 @@ tabbrowser:not([treestyletab-mode="horizontal"]) #alltabs-place-holder, /* Tab M
 tabbrowser:not([treestyletab-mode="horizontal"]) .tabs-scroll /* Tab Mix Plus */ {
 	display: none !important;
 }
-tabbrowser[treestyletab-hide-newtab-button="true"] .tabbrowser-arrowscrollbox .tabs-newtab-button /* "all tabs" button in Firefox 3 and 3.1 */ {
-	display: -moz-box !important;
-	visibility: collapse !important;
-}
 
 #appcontent {
 /*	position: relative;*/
diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index db195cbe..8a0181b4 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -23,6 +23,7 @@ var TreeStyleTabService = {
 	kFIXED              : 'treestyletab-tabbar-fixed',
 	kRESIZING           : 'treestyletab-tabbar-resizing',
 	kTRANSPARENT        : 'treestyletab-tabbar-transparent',
+	kDROP_SHADOW        : 'treestyletab-tabbar-dropshadow',
 
 	kTWISTY                : 'treestyletab-twisty',
 	kTWISTY_CONTAINER      : 'treestyletab-twisty-container',
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 7eb7ffd9..99d6b304 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -462,6 +462,7 @@ TreeStyleTabBrowser.prototype = {
 		this.observe(null, 'nsPref:changed', 'extensions.treestyletab.allowSubtreeCollapseExpand');
 		this.observe(null, 'nsPref:changed', 'extensions.treestyletab.tabbar.fixed');
 		this.observe(null, 'nsPref:changed', 'extensions.treestyletab.tabbar.transparent.style');
+		this.observe(null, 'nsPref:changed', 'extensions.treestyletab.tabbar.dropshadow');
 		window.setTimeout(function() {
 			b.treeStyleTab.observe(null, 'nsPref:changed', 'extensions.treestyletab.tabbar.autoHide.mode');
 		}, 0);
@@ -1040,6 +1041,13 @@ TreeStyleTabBrowser.prototype = {
 						this.checkTabsIndentOverflow();
 						break;
 
+					case 'extensions.treestyletab.tabbar.dropshadow':
+						if (value)
+							b.setAttribute(this.kDROP_SHADOW, true);
+						else
+							b.removeAttribute(this.kDROP_SHADOW);
+						break;
+
 					default:
 						break;
 				}
diff --git a/defaults/preferences/treestyletab.js b/defaults/preferences/treestyletab.js
index 108037ea..ff9cf9eb 100644
--- a/defaults/preferences/treestyletab.js
+++ b/defaults/preferences/treestyletab.js
@@ -28,6 +28,7 @@ pref("extensions.treestyletab.tabbar.autoShow.feedback", false);
 pref("extensions.treestyletab.tabbar.autoShow.feedback.delay", 3000);
 pref("extensions.treestyletab.tabbar.fixed", false);
 pref("extensions.treestyletab.tabbar.syncRelatedPrefsForDynamicPosition", true);
+pref("extensions.treestyletab.tabbar.dropshadow",      true);
 pref("extensions.treestyletab.enableSubtreeIndent",    true);
 pref("extensions.treestyletab.enableSubtreeIndent.allTabsPopup", true);
 pref("extensions.treestyletab.allowSubtreeCollapseExpand", true);
diff --git a/skin/classic/treestyletab/treestyletab-3.1.css b/skin/classic/treestyletab/treestyletab-3.1.css
index 8a4dfae1..ca54b309 100644
--- a/skin/classic/treestyletab/treestyletab-3.1.css
+++ b/skin/classic/treestyletab/treestyletab-3.1.css
@@ -1,20 +1,37 @@
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
+/* new-tab button */
+
+tabbrowser[treestyletab-mode="vertical"] .tabbrowser-arrowscrollbox .tabs-newtab-button {
+	border-style: none solid solid !important;
+	border-width: 0 0 1px 1px !important;
+	border-bottom: 1px solid ThreeDShadow !important;
+	-moz-border-bottom-colors: ThreeDShadow !important;
+	-moz-border-radius: 0 0 2px 2px;
+}
+tabbrowser[treestyletab-mode="vertical"][treestyletab-appearance-inverted="true"] .tabbrowser-arrowscrollbox .tabs-newtab-button {
+	border-width: 0 1px 1px 0 !important;
+}
+tabbrowser[treestyletab-mode="vertical"][treestyletab-style="vertigo"] .tabbrowser-arrowscrollbox .tabs-newtab-button {
+	border-style: none !important;
+}
+
+
 /* Shadow of vertival tabs */
 
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="default"] .tabbrowser-tab,
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="mixed"] .tabbrowser-tab {
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="default"] .tabbrowser-tab,
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="mixed"] .tabbrowser-tab {
 	-moz-box-shadow: -5px 5px 5px rgba(0, 0, 0, 0.15) !important;
 }
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="default"][treestyletab-appearance-inverted="true"] .tabbrowser-tab,
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="mixed"][treestyletab-appearance-inverted="true"] .tabbrowser-tab {
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="default"][treestyletab-appearance-inverted="true"] .tabbrowser-tab,
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="mixed"][treestyletab-appearance-inverted="true"] .tabbrowser-tab {
 	-moz-box-shadow: 5px 5px 5px rgba(0, 0, 0, 0.15) !important;
 }
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="default"]:not([treestyletab-hide-newtab-button]) .tabs-container:not([overflow="true"]) .scrollbox-innerbox,
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="mixed"]:not([treestyletab-hide-newtab-button]) .tabs-container:not([overflow="true"]) .scrollbox-innerbox {
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="default"]:not([treestyletab-hide-newtab-button]) .tabs-container:not([overflow="true"]) .scrollbox-innerbox,
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="mixed"]:not([treestyletab-hide-newtab-button]) .tabs-container:not([overflow="true"]) .scrollbox-innerbox {
 	background: url("dropshadow.png") repeat-x bottom !important;
 }
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="default"]:not([treestyletab-hide-newtab-button="true"]) .tabs-container:not([overflow="true"]) .tabbrowser-arrowscrollbox .tabs-newtab-button,
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="mixed"]:not([treestyletab-hide-newtab-button="true"]) .tabs-container:not([overflow="true"]) .tabbrowser-arrowscrollbox .tabs-newtab-button {
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="default"]:not([treestyletab-hide-newtab-button="true"]) .tabs-container:not([overflow="true"]) .tabbrowser-arrowscrollbox .tabs-newtab-button,
+tabbrowser[treestyletab-mode="vertical"][treestyletab-tabbar-dropshadow="true"][treestyletab-style="mixed"]:not([treestyletab-hide-newtab-button="true"]) .tabs-container:not([overflow="true"]) .tabbrowser-arrowscrollbox .tabs-newtab-button {
 	margin-bottom: 5px !important;
 }
diff --git a/skin/classic/treestyletab/treestyletab.css b/skin/classic/treestyletab/treestyletab.css
index ec85dd5b..016ad61c 100644
--- a/skin/classic/treestyletab/treestyletab.css
+++ b/skin/classic/treestyletab/treestyletab.css
@@ -414,7 +414,6 @@ tabbrowser[treestyletab-tabbar-position="bottom"] .tabbrowser-tab[treestyletab-d
 
 /* vertical tab bar */
 
-/* Firefox 2 or later */
 tabbrowser[treestyletab-mode="vertical"] .tabs-alltabs-stack > hbox {
 	position: static !important;
 }
@@ -445,21 +444,6 @@ tabbrowser[treestyletab-mode="vertical"] .tabs-alltabs-button {
 	height: 16px !important;
 }
 
-/* Firefox 3.1 new-tab button */
-tabbrowser[treestyletab-mode="vertical"] .tabbrowser-arrowscrollbox .tabs-newtab-button {
-	border-style: none solid solid !important;
-	border-width: 0 0 1px 1px !important;
-	border-bottom: 1px solid ThreeDShadow !important;
-	-moz-border-bottom-colors: ThreeDShadow !important;
-	-moz-border-radius: 0 0 2px 2px;
-}
-tabbrowser[treestyletab-mode="vertical"][treestyletab-appearance-inverted="true"] .tabbrowser-arrowscrollbox .tabs-newtab-button {
-	border-width: 0 1px 1px 0 !important;
-}
-tabbrowser[treestyletab-mode="vertical"][treestyletab-style="vertigo"] .tabbrowser-arrowscrollbox .tabs-newtab-button {
-	border-style: none !important;
-}
-
 
 /* transaprent tab bar */
 tabbrowser[treestyletab-tabbar-transparent] .tabbrowser-tab {