diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index 7fb7c491..72c5fbcf 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -6,6 +6,7 @@ var TreeStyleTabService = {
 	kINSERT_BEFORE      : 'treestyletab-insert-before',
 	kSUBTREE_COLLAPSED  : 'treestyletab-subtree-collapsed',
 	kCOLLAPSED          : 'treestyletab-collapsed',
+	kTWISTY_HOVER       : 'treestyletab-twisty-hover',
 	kNEST               : 'treestyletab-nest',
 	kDROP_POSITION      : 'treestyletab-drop-position',
 	kTABBAR_POSITION    : 'treestyletab-tabbar-position',
@@ -25,6 +26,7 @@ var TreeStyleTabService = {
 	kCOUNTER               : 'treestyletab-counter',
 	kCOUNTER_CONTAINER     : 'treestyletab-counter-container',
 	kSPLITTER              : 'treestyletab-splitter',
+	kSTRINGBUNDLE          : 'treestyletab-stringbundle',
 
 	kMENUITEM_REMOVESUBTREE_SELECTION : 'multipletab-selection-item-removeTabSubTree',
 
@@ -106,6 +108,14 @@ var TreeStyleTabService = {
 		return this._XULAppInfo;
 	},
 	_XULAppInfo : null,
+
+	get stringbundle() {
+		if (!this._stringbundle) {
+			this._stringbundle = document.getElementById(this.kSTRINGBUNDLE);
+		}
+		return this._stringbundle;
+	},
+	_stringbundle : null,
 	 
 /* API */ 
 	
diff --git a/content/treestyletab/treestyletab.xul b/content/treestyletab/treestyletab.xul
index 212adb50..b4cc6412 100644
--- a/content/treestyletab/treestyletab.xul
+++ b/content/treestyletab/treestyletab.xul
@@ -29,6 +29,11 @@
 		oncommand="TreeStyleTabService.removeTabSubTree(MultipleTabService.getSelectedTabs());"/>
 </menupopup>
 
+<stringbundleset id="stringbundleset">
+	<stringbundle id="treestyletab-stringbundle"
+		src="chrome://treestyletab/locale/treestyletab.properties"/>
+</stringbundleset>
+
 <window id="main-window">
 	<data id="multipletab-tabcontext-menu-template" collapsed="true">
 		<menuitem id="context-item-removeTabSubTree"
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 2a7f2691..7edb7617 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -93,6 +93,8 @@ TreeStyleTabBrowser.prototype = {
 		b.mStrip.addEventListener('dragexit', this, false);
 		b.mStrip.addEventListener('dragover', this, false);
 		b.mStrip.addEventListener('dragdrop', this, false);
+		b.mTabContainer.addEventListener('mouseover', this, true);
+		b.mTabContainer.addEventListener('mouseout', this, true);
 		b.mTabContainer.addEventListener('click', this, true);
 		b.mTabContainer.addEventListener('dblclick', this, true);
 		b.mTabContainer.addEventListener('mousedown', this, true);
@@ -296,6 +298,27 @@ TreeStyleTabBrowser.prototype = {
 			)
 		);
 
+		eval('b.createTooltip = '+
+			b.createTooltip.toSource().replace(
+				'if (tn.hasAttribute("label")) {',
+				<><![CDATA[
+					else if (tn.getAttribute(TreeStyleTabService.kTWISTY_HOVER) == 'true') {
+						var key = tn.getAttribute(TreeStyleTabService.kSUBTREE_COLLAPSED) == 'true' ? 'tooltip.expandSubtree' : 'tooltip.collapseSubtree' ;
+						event.target.setAttribute(
+							'label',
+							tn.hasAttribute('label') ?
+								TreeStyleTabService.stringbundle.getFormattedString(
+									key+'.labeled',
+									[tn.getAttribute('label')]
+								) :
+								TreeStyleTabService.stringbundle.getString(key)
+						);
+						return true;
+					}
+					$&]]></>
+			)
+		);
+
 		var tabs = b.mTabContainer.childNodes;
 		for (var i = 0, maxi = tabs.length; i < maxi; i++)
 		{
@@ -925,6 +948,18 @@ TreeStyleTabBrowser.prototype = {
 			case 'dragdrop':
 				nsDragAndDrop.drop(aEvent, this);
 				return;
+
+			case 'mouseover':
+				if (this.isEventFiredOnTwisty(aEvent)) {
+					aEvent.target.setAttribute(this.kTWISTY_HOVER, true);
+				}
+				return;
+
+			case 'mouseout':
+				if (this.isEventFiredOnTwisty(aEvent)) {
+					aEvent.target.removeAttribute(this.kTWISTY_HOVER);
+				}
+				return;
 		}
 	},
  
diff --git a/install.rdf b/install.rdf
index ec4aaca3..c67ca6e6 100644
--- a/install.rdf
+++ b/install.rdf
@@ -5,10 +5,10 @@
   <RDF:Description RDF:about="urn:mozilla:install-manifest"
                    em:id="treestyletab@piro.sakura.ne.jp"
                    em:name="Tree Style Tab"
-                   em:version="0.5.2007113001"
+                   em:version="0.5.2007120101"
                    em:creator="SHIMODA Hiroshi"
                    em:description="Show tabs like a tree."
-                   em:homepageURL="http://piro.sakura.ne.jp/xul/treestyletab/"
+                   em:homepageURL="http://piro.sakura.ne.jp/xul/_treestyletab.html.en"
                    em:iconURL="chrome://treestyletab/content/res/icon32.png"
                    em:optionsURL="chrome://treestyletab/content/config.xul">
   <em:translator>Godai71.Extenzilla (it-IT locale)</em:translator>
@@ -26,7 +26,8 @@
     <em:localized>
       <RDF:Description em:locale="ja"
                        em:name="ツリー型タブ"
-                       em:description="タブをツリー状に表示します。"/>
+                       em:description="タブをツリー状に表示します。"
+                       em:homepageURL="http://piro.sakura.ne.jp/xul/_treestyletab.html"/>
     </em:localized>
     <em:localized>
       <RDF:Description em:locale="it-IT"
diff --git a/locale/en-US/treestyletab/treestyletab.properties b/locale/en-US/treestyletab/treestyletab.properties
index 2bcf7640..55bd43de 100644
--- a/locale/en-US/treestyletab/treestyletab.properties
+++ b/locale/en-US/treestyletab/treestyletab.properties
@@ -1,2 +1,7 @@
 extensions.treestyletab@piro.sakura.ne.jp.name=Tree Style Tab
 extensions.treestyletab@piro.sakura.ne.jp.description=Show tabs like a tree.
+
+tooltip.collapseSubtree=Collapse Tree
+tooltip.collapseSubtree.labeled=Collapse Tree ( %S )
+tooltip.expandSubtree=Expand Tree
+tooltip.expandSubtree.labeled=Expand Tree ( %S )
diff --git a/locale/it-IT/treestyletab/treestyletab.properties b/locale/it-IT/treestyletab/treestyletab.properties
index c45f7829..4a6ab4ef 100644
--- a/locale/it-IT/treestyletab/treestyletab.properties
+++ b/locale/it-IT/treestyletab/treestyletab.properties
@@ -1,2 +1,7 @@
 extensions.treestyletab@piro.sakura.ne.jp.name=Tree Style Tab
 extensions.treestyletab@piro.sakura.ne.jp.description=Permette di visualizzare la barra delle schede in forma di albero
+
+tooltip.collapseSubtree=Contrai tutti
+tooltip.collapseSubtree.labeled=Contrai tutti ( %S )
+tooltip.expandSubtree=Espandi tutti
+tooltip.expandSubtree.labeled=Espandi tutti ( %S )
diff --git a/locale/ja/treestyletab/treestyletab.properties b/locale/ja/treestyletab/treestyletab.properties
index 8ac78527..4741075b 100644
--- a/locale/ja/treestyletab/treestyletab.properties
+++ b/locale/ja/treestyletab/treestyletab.properties
@@ -1,2 +1,7 @@
 extensions.treestyletab@piro.sakura.ne.jp.name=ツリー型タブ
 extensions.treestyletab@piro.sakura.ne.jp.description=タブをツリー状に表示します。
+
+tooltip.collapseSubtree=ツリーをたたむ
+tooltip.collapseSubtree.labeled=ツリーをたたむ（ %S ）
+tooltip.expandSubtree=ツリーを展開する
+tooltip.expandSubtree.labeled=ツリーを展開する（ %S ）
diff --git a/skin/classic/treestyletab/tree-twisty-collapsed.png b/skin/classic/treestyletab/tree-twisty-collapsed.png
deleted file mode 100644
index ae95169e..00000000
Binary files a/skin/classic/treestyletab/tree-twisty-collapsed.png and /dev/null differ
diff --git a/skin/classic/treestyletab/tree-twisty-expanded.png b/skin/classic/treestyletab/tree-twisty-expanded.png
deleted file mode 100644
index 4c958430..00000000
Binary files a/skin/classic/treestyletab/tree-twisty-expanded.png and /dev/null differ
diff --git a/skin/classic/treestyletab/tree-twisty.png b/skin/classic/treestyletab/tree-twisty.png
new file mode 100644
index 00000000..2a2e6994
Binary files /dev/null and b/skin/classic/treestyletab/tree-twisty.png differ
diff --git a/skin/classic/treestyletab/treestyletab.css b/skin/classic/treestyletab/treestyletab.css
index b9f85381..9a962f81 100644
--- a/skin/classic/treestyletab/treestyletab.css
+++ b/skin/classic/treestyletab/treestyletab.css
@@ -264,11 +264,18 @@ tabbrowser:not([treestyletab-mode="vertical"])[treestyletab-allow-subtree-collap
 }
 
 .treestyletab-twisty {
-	list-style-image: url("tree-twisty-expanded.png");
+	list-style-image: url("tree-twisty.png");
+	-moz-image-region: rect(0, 32px, 16px, 16px);
+}
+.tabbrowser-tab[treestyletab-subtree-collapsed="true"] .treestyletab-twisty {
+	-moz-image-region: rect(0, 16px, 16px, 0);
 }
 
-.tabbrowser-tab[treestyletab-subtree-collapsed="true"] .treestyletab-twisty {
-	list-style-image: url("tree-twisty-collapsed.png");
+.tabbrowser-tab[treestyletab-twisty-hover="true"] .treestyletab-twisty {
+	-moz-image-region: rect(16px, 32px, 32px, 16px);
+}
+.tabbrowser-tab[treestyletab-subtree-collapsed="true"][treestyletab-twisty-hover="true"] .treestyletab-twisty {
+	-moz-image-region: rect(16px, 16px, 32px, 0);
 }
 
 .treestyletab-counter-container {