diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index 840b88a2..a1384274 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -23,3 +23,7 @@ tabbrowser[treestyletab-vertical="true"] .tabs-alltabs-stack,
 tabbrowser[treestyletab-vertical="true"] .tabs-closebutton-box {
 	display: none !important;
 }
+
+tabbrowser[treestyletab-vertical="true"] > tabbox {
+	-moz-box-orient: horizontal !important;
+}
diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index 3f927527..8d2047e3 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -115,7 +115,7 @@ var TreeStyleTabService = {
  
 	get browser() 
 	{
-		return 'SplitBrowser' ? SplitBrowser.activeBrowser : gBrowser ;
+		return 'SplitBrowser' && this.getPref('extensions.treestyletab.inSubbrowsers.enabled')  ? SplitBrowser.activeBrowser : gBrowser ;
 	},
  
 	evaluateXPath : function(aExpression, aContext, aType) 
@@ -227,9 +227,11 @@ var TreeStyleTabService = {
 
 		window.removeEventListener('load', this, false);
 
-		var appcontent = document.getElementById('appcontent');
-		appcontent.addEventListener('SubBrowserAdded', this, false);
-		appcontent.addEventListener('SubBrowserRemoveRequest', this, false);
+		if (this.getPref('extensions.treestyletab.inSubbrowsers.enabled')) {
+			var appcontent = document.getElementById('appcontent');
+			appcontent.addEventListener('SubBrowserAdded', this, false);
+			appcontent.addEventListener('SubBrowserRemoveRequest', this, false);
+		}
 
 		this.addPrefListener(this);
 		this.observe(null, 'nsPref:changed', 'extensions.treestyletab.levelMargin');
@@ -665,9 +667,11 @@ catch(e) {
 
 		window.removeEventListener('unload', this, false);
 
-		var appcontent = document.getElementById('appcontent');
-		appcontent.removeEventListener('SubBrowserAdded', this, false);
-		appcontent.removeEventListener('SubBrowserRemoveRequest', this, false);
+		if (this.getPref('extensions.treestyletab.inSubbrowsers.enabled')) {
+			var appcontent = document.getElementById('appcontent');
+			appcontent.removeEventListener('SubBrowserAdded', this, false);
+			appcontent.removeEventListener('SubBrowserRemoveRequest', this, false);
+		}
 
 		this.removePrefListener(this);
 
diff --git a/defaults/preferences/treestyletab.js b/defaults/preferences/treestyletab.js
index ba3ebfa5..1388cd28 100644
--- a/defaults/preferences/treestyletab.js
+++ b/defaults/preferences/treestyletab.js
@@ -13,6 +13,7 @@ pref("browser.link.open_newwindow.restriction", 0);
 
 pref("extensions.multipletab.show.multipletab-selection-item-removeTabSubTree", true);
 pref("extensions.multipletab.show.context-item-removeTabSubTree", true);
+pref("extensions.treestyletab.inSubbrowsers.enabled", false);
 
 
 pref("extensions.treestyletab@piro.sakura.ne.jp.name", "chrome://treestyletab/locale/treestyletab.properties");