diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index b9755198..5b96e4ba 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -25,11 +25,12 @@
 .tabbrowser-strip[treestyletab-tabbar-autohide="hidden"]+splitter,
 tabbrowser:not([treestyletab-tabbar-autohide="hidden"]) .treestyletab-tabbar-toggler,
 #TabsToolbar[treestyletab-tabbar-autohide="hidden"] > *,
-#TabsToolbar:not([treestyletab-tabbar-autohide-state="expanded"]) #treestyletab-tabbar-resizer-box,
+#TabsToolbar #treestyletab-tabbar-resizer-box,
 #appcontent[ahFull="true"] .tabbrowser-strip[ahHIDE="true"]+splitter /* AutoHide */,
 .tabbrowser-strip[treestyletab-tabbar-fixed="true"]+splitter,
 .tabbrowser-strip[treestyletab-print-preview="true"],
 .tabbrowser-strip[treestyletab-print-preview="true"]+splitter,
+#TabsToolbar .treestyletab-splitter,
 #TabsToolbar[treestyletab-print-preview="true"],
 window[chromehidden~="toolbar"] .tabbrowser-strip[treestyletab-tabbar-placeholder="true"],
 window[chromehidden~="toolbar"] .tabbrowser-strip[treestyletab-tabbar-placeholder="true"]+splitter {
@@ -114,19 +115,31 @@ tabbrowser[treestyletab-mode="vertical"] .tabs-stack > *:first-child + * > hbox:
 	overflow: hidden !important;
 }
 
-#TabsToolbar[treestyletab-tabbar-autohide-state="expanded"] > *,
-.tabs-toolbar-inner-box[treestyletab-tabbar-autohide-state="expanded"] > * {
+#TabsToolbar[treestyletab-mode="vertical"][treestyletab-tabbar-autohide][treestyletab-tabbar-autohide-state="expanded"]
+  > *,
+.tabs-toolbar-inner-box[treestyletab-tabbar-autohide][treestyletab-tabbar-autohide-state="expanded"]:not([treestyletab-tabbar-fixed="true"])
+  > * {
 	position: relative;
 	z-index: 2;
 }
-#TabsToolbar[treestyletab-tabbar-autohide-state="expanded"] #treestyletab-tabbar-resizer-box {
+#TabsToolbar[treestyletab-mode="vertical"][treestyletab-tabbar-autohide][treestyletab-tabbar-autohide-state="expanded"]
+  #treestyletab-tabbar-resizer-box {
 	position: absolute;
 	bottom: 0;
 	left: 0;
 	right: 0;
 	top: 0;
 	z-index: 1;
+	line-height: 0; /* to avoid an useless space above the splitter */
+	font-size: 0; /* to avoid an useless space above the splitter */
 }
+#TabsToolbar[treestyletab-mode="vertical"][treestyletab-tabbar-autohide][treestyletab-tabbar-autohide-state="expanded"]
+  #treestyletab-tabbar-resizer-box,
+#TabsToolbar[treestyletab-mode="vertical"][treestyletab-tabbar-autohide][treestyletab-tabbar-autohide-state="expanded"]:not([treestyletab-tabbar-fixed="true"])
+  .treestyletab-splitter {
+	visibility: visible;
+}
+
 
 
 
diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index b4f1463e..2a4a6308 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -333,7 +333,7 @@ var TreeStyleTabService = {
 		window.removeEventListener('load', this, false);
 		window.addEventListener('unload', this, false);
 		document.addEventListener('popupshowing', this, false);
-		document.addEventListener('popuphiding', this, false);
+		document.addEventListener('popuphiding', this, true);
 		document.addEventListener('TreeStyleTabCollapsedStateChange', this, false);
 		document.addEventListener('TreeStyleTabTabbarPositionChanged', this, false);
 		document.addEventListener('TreeStyleTabTabbarStateChanged', this, false);
@@ -1358,7 +1358,7 @@ catch(e) {
 			this.endListenKeyEventsFor(this.LISTEN_FOR_AUTOEXPAND_BY_FOCUSCHANGE);
 
 			document.removeEventListener('popupshowing', this, false);
-			document.removeEventListener('popuphiding', this, false);
+			document.removeEventListener('popuphiding', this, true);
 			document.removeEventListener('TreeStyleTabCollapsedStateChange', this, false);
 			document.removeEventListener('TreeStyleTabTabbarPositionChanged', this, false);
 			document.removeEventListener('TreeStyleTabTabbarStateChanged', this, false);
@@ -1411,34 +1411,13 @@ catch(e) {
 				return this.onTabRestored(aEvent);
 
 			case 'popupshowing':
-				if (aEvent.originalTarget.boxObject &&
-					!this.evaluateXPath(
-						'local-name() = "tooltip" or local-name() ="panel" or '+
-						'parent::*/ancestor-or-self::*[local-name()="popup" or local-name()="menupopup"]',
-						aEvent.originalTarget,
-						XPathResult.BOOLEAN_TYPE
-					).booleanValue) {
-					this.popupMenuShown = true;
-					window.setTimeout(function(aSelf, aPopup) {
-						if (!aPopup.boxObject.width || !aPopup.boxObject.height)
-							aSelf.popupMenuShown = false;
-					}, 10, this, aEvent.originalTarget);
-				}
+				this.onPopupShown(aEvent.originalTarget);
 				if ((aEvent.originalTarget.getAttribute('anonid') || aEvent.originalTarget.id) == 'alltabs-popup')
 					this.updateAllTabsPopup(aEvent);
 				return;
 
 			case 'popuphiding':
-				if (aEvent.originalTarget.boxObject &&
-					!this.evaluateXPath(
-						'local-name() = "tooltip" or local-name() ="panel" or '+
-						'parent::*/ancestor-or-self::*[local-name()="popup" or local-name()="menupopup"]',
-						aEvent.originalTarget,
-						XPathResult.BOOLEAN_TYPE
-					).booleanValue) {
-					this.popupMenuShown = false;
-				}
-				return;
+				return this.onPopupHidden(aEvent.originalTarget);
 
 			case 'TreeStyleTabCollapsedStateChange':
 				return this.updateAeroPeekPreviews();
@@ -1618,25 +1597,30 @@ catch(e) {
    
 	onTabbarResized : function TSTService_onTabbarResized(aEvent) 
 	{
-		var b = this.getTabBrowserFromChild(aEvent.currentTarget);
-		var box = (b.treeStyleTab.tabStripPlaceHolder || this.getTabStrip(b)).boxObject;
+		var target = aEvent.currentTarget;
+		var b = this.getTabBrowserFromChild(target);
+		var strip = this.getTabStrip(b);
+		var box = (b.treeStyleTab.tabStripPlaceHolder || strip).boxObject;
 		window.setTimeout(function(aSelf) {
 			if (!b.treeStyleTab.clickedOnTabbarResizerGrippy) {
 				if (!b.treeStyleTab.isVertical) {
-					aSelf.setTreePref('tabbar.height', aSelf.maxTabbarHeight(box.height, b));
+					let height = aSelf.maxTabbarHeight(box.height, b);
+					aSelf.setTreePref('tabbar.height', height);
 				}
 				else {
+					let width = aSelf.maxTabbarWidth(box.width, b);
 					if (!b.treeStyleTab.autoHide.expanded)
-						aSelf.setTreePref('tabbar.shrunkenWidth', aSelf.maxTabbarWidth(box.width, b));
+						aSelf.setTreePref('tabbar.shrunkenWidth', width);
 					else
-						aSelf.setTreePref('tabbar.width', aSelf.maxTabbarWidth(box.width, b));
+						aSelf.setTreePref('tabbar.width', width);
 				}
 			}
-			b.treeStyleTab.updateFloatingTabbar();
+			b.treeStyleTab.updateFloatingTabbar(true);
 			b.treeStyleTab.clickedOnTabbarResizerGrippy = false;
 		}, 10, this);
 	},
-	onTabbarResizerClick : function TSTService_onTabbarResizerClick(aEvent)
+ 
+	onTabbarResizerClick : function TSTService_onTabbarResizerClick(aEvent) 
 	{
 		var b = this.getTabBrowserFromChild(aEvent.currentTarget);
 		b.treeStyleTab.clickedOnTabbarResizerGrippy = this.evaluateXPath(
@@ -1646,6 +1630,59 @@ catch(e) {
 			).booleanValue;
 	},
  
+	onFloatingTabbarResizeStart : function TSTService_onFloatingTabbarResizeStart(aEvent) 
+	{
+		aEvent.stopPropagation();
+		aEvent.target.setCapture(true);
+		this.floatingTabbarResizeResizing = true;
+		var b = this.getTabBrowserFromChild(aEvent.target);
+		var strip = this.getTabStrip(b);
+		this.floatingTabbarResizeStartWidth  = strip.boxObject.width;
+		this.floatingTabbarResizeStartHeight = strip.boxObject.height;
+		this.floatingTabbarResizeStartX = aEvent.screenX;
+		this.floatingTabbarResizeStartY = aEvent.screenY;
+	},
+	onFloatingTabbarResizeEnd : function TSTService_onFloatingTabbarResizeEnd(aEvent)
+	{
+		aEvent.stopPropagation();
+		aEvent.target.releaseCapture();
+		this.floatingTabbarResizeResizing = false;
+		this.floatingTabbarResizeStartWidth  = -1;
+		this.floatingTabbarResizeStartHeight = -1;
+		this.floatingTabbarResizeStartX = -1;
+		this.floatingTabbarResizeStartY = -1;
+	},
+	onFloatingTabbarResizing : function TSTService_onFloatingTabbarResizing(aEvent)
+	{
+		if (!this.floatingTabbarResizeResizing)
+			return;
+
+		aEvent.stopPropagation();
+		var b = this.getTabBrowserFromChild(aEvent.target);
+		var width = this.floatingTabbarResizeStartWidth;
+		var height = this.floatingTabbarResizeStartHeight;
+		var pos = b.treeStyleTab.currentTabbarPosition;
+		if (b.treeStyleTab.isVertical) {
+			let delta = aEvent.screenX - this.floatingTabbarResizeStartX;
+			width += (pos == 'left' ? delta : -delta );
+			this.setTreePref('tabbar.width', Math.max(0, width));
+			if (b.treeStyleTab.autoHide.mode == b.treeStyleTab.autoHide.kMODE_SHRINK &&
+				b.treeStyleTab._tabStripPlaceHolder)
+				b.treeStyleTab._tabStripPlaceHolder.setAttribute('width', this.getTreePref('tabbar.shrunkenWidth'));
+		}
+		else {
+			let delta = aEvent.screenY - this.floatingTabbarResizeStartY;
+			height += (pos == 'top' ? delta : -delta );
+			this.setTreePref('tabbar.height', Math.max(0, height));
+		}
+		b.treeStyleTab.updateFloatingTabbar(true);
+	},
+	floatingTabbarResizeResizing : false,
+	floatingTabbarResizeStartWidth  : -1,
+	floatingTabbarResizeStartHeight : -1,
+	floatingTabbarResizeStartX : -1,
+	floatingTabbarResizeStartY : -1,
+ 
 	showHideSubtreeMenuItem : function TSTService_showHideSubtreeMenuItem(aMenuItem, aTabs) 
 	{
 		if (!aMenuItem ||
@@ -1782,6 +1819,49 @@ catch(e) {
 			delete this._tabsOnTopDefaultState;
 		}
 	},
+ 
+	onPopupShown : function TSTService_onPopupShown(aPopup) 
+	{
+		if (!aPopup.boxObject ||
+			this.evaluateXPath(
+				'local-name() = "tooltip" or local-name() ="panel" or '+
+				'parent::*/ancestor-or-self::*[local-name()="popup" or local-name()="menupopup"]',
+				aEvent.originalTarget,
+				XPathResult.BOOLEAN_TYPE
+			).booleanValue)
+			return;
+
+		window.setTimeout(function(aSelf) {
+			if (!aPopup.boxObject.width && !aPopup.boxObject.height)
+				return;
+
+			var id = aPopup.id;
+			var item = document.getElementById(id) ? id : aPopup ;
+			var index = TreeStyleTabService._shownPopups.indexOf(item);
+			if (index < 0)
+				TreeStyleTabService._shownPopups.push(item);
+		}, 10, this);
+	},
+ 
+	onPopupHidden : function TSTService_onPopupHidden(aPopup) 
+	{
+		var id = aPopup.id;
+		aPopup = document.getElementById(id) || aPopup;
+		var index = TreeStyleTabService._shownPopups.indexOf(aPopup);
+		if (index > -1)
+			TreeStyleTabService._shownPopups.splice(index, 1);
+	},
+ 
+	isPopupShown : function TSTService_isPopupShown() 
+	{
+		TreeStyleTabService._shownPopups = TreeStyleTabService._shownPopups.filter(function(aItem) {
+			if (typeof aItem == 'string')
+				aItem = document.getElementById(aItem);
+			return aItem && aItem.boxObject && aItem.boxObject.width && aItem.boxObject.height;
+		});
+		return TreeStyleTabService._shownPopups.length > 0;
+	},
+	_shownPopups : [],
   
 /* Tree Style Tabの初期化が行われる前に復元されたセッションについてツリー構造を復元 */ 
 	
diff --git a/content/treestyletab/treestyletab.xul b/content/treestyletab/treestyletab.xul
index f681402d..c41c06cb 100644
--- a/content/treestyletab/treestyletab.xul
+++ b/content/treestyletab/treestyletab.xul
@@ -148,8 +148,14 @@
 </popupset>
 
 <toolbar id="TabsToolbar">
-	<hbox id="treestyletab-tabbar-resizer-box">
-	</hbox>
+	<box id="treestyletab-tabbar-resizer-box">
+		<splitter id="treestyletab-tabbar-resizer-splitter"
+			class="treestyletab-splitter"
+			onmousedown="TreeStyleTabService.onFloatingTabbarResizeStart(event);"
+			onmouseup="TreeStyleTabService.onFloatingTabbarResizeEnd(event);"
+			onmousemove="TreeStyleTabService.onFloatingTabbarResizing(event);"
+			dblclick="gBrowser.treeStyleTab.resetTabbarSize(); event.stopPropagation();"/>
+	</box>
 </toolbar>
 
 </overlay>
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index f66bb9d2..cf9e788c 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -743,7 +743,7 @@ TreeStyleTabBrowser.prototype = {
 
 		this.autoHide;
 
-		this.fireTabbarPositionEvent('TreeStyleTabTabbarPositionChanged', 'top', position); /* PUBLIC API */
+		this.fireTabbarPositionEvent(false, 'top', position); /* PUBLIC API */
 
 		b = null;
 
@@ -1263,7 +1263,7 @@ TreeStyleTabBrowser.prototype = {
 		}, 0, this.mTabBrowser);
 	},
  
-	updateFloatingTabbar : function TSTBrowser_updateFloatingTabbar(aWidth, aHeight, aJustNow) 
+	updateFloatingTabbar : function TSTBrowser_updateFloatingTabbar(aJustNow) 
 	{
 		// this method is just for Firefox 4.0 or later
 		if (!this.isFloating) return;
@@ -1274,16 +1274,16 @@ TreeStyleTabBrowser.prototype = {
 		}
 
 		if (aJustNow) {
-			this.updateFloatingTabbarInternal(aWidth, aHeight);
+			this.updateFloatingTabbarInternal();
 		}
 		else {
 			this.updateFloatingTabbarTimer = window.setTimeout(function(aSelf) {
 				aSelf.updateFloatingTabbarTimer = null;
-				aSelf.updateFloatingTabbarInternal(aWidth, aHeight)
+				aSelf.updateFloatingTabbarInternal()
 			}, 0, this);
 		}
 	},
-	updateFloatingTabbarInternal : function TSTBrowser_updateFloatingTabbarInternal(aWidth, aHeight)
+	updateFloatingTabbarInternal : function TSTBrowser_updateFloatingTabbarInternal()
 	{
 		var strip = this.tabStrip;
 		var tabContainerBox = this.getTabContainerBox(this.mTabBrowser);
@@ -1298,8 +1298,8 @@ TreeStyleTabBrowser.prototype = {
 
 			let realWidth = parseInt(this._tabStripPlaceHolder.getAttribute('width') || box.width);
 			let realHeight = parseInt(this._tabStripPlaceHolder.getAttribute('height') || box.height);
-			let width = aWidth || realWidth;
-			let height = aHeight || realHeight;
+			let width = (this.autoHide.expanded && this.isVertical ? this.maxTabbarWidth(this.getTreePref('tabbar.width')) : 0 ) || realWidth;
+			let height = (this.autoHide.expanded && !this.isVertical ? this.maxTabbarHeight(this.getTreePref('tabbar.height')) : 0 ) || realHeight;
 			let xOffset = pos == 'right' ? width - realWidth : 0 ;
 			let yOffset = pos == 'bottom' ? height - realHeight : 0 ;
 
@@ -1309,11 +1309,12 @@ TreeStyleTabBrowser.prototype = {
 			strip.style.width = (tabContainerBox.width = width)+'px';
 			strip.style.height = (tabContainerBox.height = height)+'px';
 
-			let resizerStyle = this.floatingTabbarResizerBox.style;
-			resizerStyle.top    = pos == 'top' ? realHeight+'px' : '' ;
-			resizerStyle.right  = pos == 'right' ? realWidth+'px' : '' ;
-			resizerStyle.left   = pos == 'left' ? realWidth+'px' : '' ;
-			resizerStyle.bottom = pos == 'bottom' ? realHeight+'px' : '' ;
+			this.updateFloatingTabbarResizer({
+				width      : width,
+				realWidth  : realWidth,
+				height     : height,
+				realHeight : realHeight
+			});
 
 			tabContainerBox.collapsed = (this.splitter && this.splitter.getAttribute('state') == 'collapsed');
 
@@ -1366,9 +1367,52 @@ TreeStyleTabBrowser.prototype = {
 		if ('_positionPinnedTabs' in this.mTabBrowser.mTabContainer)
 			this.mTabBrowser.mTabContainer._positionPinnedTabs();
 	},
-	get floatingTabbarResizerBox()
+	updateFloatingTabbarResizer : function TSTBrowser_updateFloatingTabbarResizer(aSize)
 	{
-		return document.getElementById('treestyletab-tabbar-resizer-box');
+		var width      = aSize.width;
+		var realWidth  = aSize.realWidth;
+		var height     = aSize.height;
+		var realHeight = aSize.realHeight;
+		var pos        = this.currentTabbarPosition;
+		var vertical = this.isVertical;
+
+		var splitter = document.getElementById('treestyletab-tabbar-resizer-splitter');
+		var box = splitter.parentNode;
+
+		box.orient = splitter.orient = vertical ? 'horizontal' : 'vertical' ;
+		box.width = (width - realWidth) || width;
+		box.height = (height - realHeight) || height;
+
+		var boxStyle = box.style;
+		boxStyle.top    = pos == 'top' ? realHeight+'px' : '' ;
+		boxStyle.right  = pos == 'right' ? realWidth+'px' : '' ;
+		boxStyle.left   = pos == 'left' ? realWidth+'px' : '' ;
+		boxStyle.bottom = pos == 'bottom' ? realHeight+'px' : '' ;
+
+		if (vertical) {
+			splitter.removeAttribute('width');
+			splitter.setAttribute('height', height);
+		}
+		else {
+			splitter.setAttribute('width', width);
+			splitter.removeAttribute('height');
+		}
+
+		var splitterWidth = splitter.boxObject.width;
+		var splitterHeight = splitter.boxObject.height;
+		var splitterStyle = splitter.style;
+		splitterStyle.marginTop    = pos == 'bottom' ? (-splitterHeight)+'px' :
+									vertical ? '0' :
+									box.height+'px' ;
+		splitterStyle.marginRight  = pos == 'left' ? (-splitterWidth)+'px' :
+									!vertical ? '0' :
+									box.width+'px' ;
+		splitterStyle.marginLeft   = pos == 'right' ? (-splitterWidth)+'px' :
+									!vertical ? '0' :
+									box.width+'px' ;
+		splitterStyle.marginBottom = pos == 'top' ? (-splitterHeight)+'px' :
+									vertical ? '0' :
+									box.height+'px' ;
 	},
  
 	resetTabbarSize : function TSTBrowser_resetTabbarSize() 
diff --git a/content/treestyletab/treestyletabbrowser_autoHide.js b/content/treestyletab/treestyletabbrowser_autoHide.js
index bacc37cf..5bddf667 100644
--- a/content/treestyletab/treestyletabbrowser_autoHide.js
+++ b/content/treestyletab/treestyletabbrowser_autoHide.js
@@ -191,10 +191,13 @@ TreeStyleTabBrowserAutoHide.prototype = {
 		this.clearBG();
 		this.updateTransparency();
 
-		sv.container.style.margin = 0;
+		if (!sv.isFloating)
+			sv.container.style.margin = 0;
 		sv.removeTabbrowserAttribute(this.kAUTOHIDE);
 		sv.removeTabbrowserAttribute(this.kSTATE);
 		sv.removeTabbrowserAttribute(this.kTRANSPARENT);
+
+		sv.setTabStripAttribute('width', this.widthFromMode);
 	},
  
 	// fullscreen 
@@ -540,7 +543,11 @@ TreeStyleTabBrowserAutoHide.prototype = {
 		switch (this.mode)
 		{
 			case this.kMODE_DISABLED:
+				break;
+
 			case this.kMODE_HIDE:
+				if (sv.isFloating)
+					sv.updateFloatingTabbar(true);
 				break;
 
 			default:
@@ -548,7 +555,7 @@ TreeStyleTabBrowserAutoHide.prototype = {
 				if (pos == 'left' || pos == 'right') {
 					let width = sv.maxTabbarWidth(this.getTreePref('tabbar.width'));
 					if (sv.isFloating) // Firefox 4.0-
-						sv.updateFloatingTabbar(width, 0, true);
+						sv.updateFloatingTabbar(true);
 					else // -Firefox 3.6
 						sv.setTabStripAttribute('width', width);
 				}
@@ -575,19 +582,23 @@ TreeStyleTabBrowserAutoHide.prototype = {
 		switch (this.mode)
 		{
 			case this.kMODE_DISABLED:
+				sv.setTabbrowserAttribute(this.kAUTOHIDE, 'hidden');
+				sv.setTabbrowserAttribute(this.kSTATE, this.kSTATE_HIDDEN);
+				break;
+
 			case this.kMODE_HIDE:
 				sv.setTabbrowserAttribute(this.kAUTOHIDE, 'hidden');
 				sv.setTabbrowserAttribute(this.kSTATE, this.kSTATE_HIDDEN);
+				sv.updateFloatingTabbar(true);
 				break;
 
 			default:
 			case this.kMODE_SHRINK:
 				sv.setTabbrowserAttribute(this.kAUTOHIDE, 'show');
 				sv.setTabbrowserAttribute(this.kSTATE, this.kSTATE_SHRUNKEN);
-				if (pos == 'left' || pos == 'right') {
+				if (pos == 'left' || pos == 'right')
 					sv.setTabStripAttribute('width', this.getTreePref('tabbar.shrunkenWidth'));
-					sv.updateFloatingTabbar(0, 0, true);
-				}
+				sv.updateFloatingTabbar(true);
 				break;
 		}
 	},
@@ -871,6 +882,7 @@ TreeStyleTabBrowserAutoHide.prototype = {
 		else {
 			sv.removeTabbrowserAttribute(this.kTRANSPARENT);
 		}
+		sv.updateFloatingTabbar();
 	},
   
 	// event handling 
@@ -1004,7 +1016,10 @@ TreeStyleTabBrowserAutoHide.prototype = {
 				return;
 
 			case 'TreeStyleTabTabbarPositionChanged':
-				if (this.enabled) this.show();
+				if (this.enabled) {
+					this.hide();
+					this.show();
+				}
 				this.updateTransparency();
 				return;
 
@@ -1113,7 +1128,7 @@ TreeStyleTabBrowserAutoHide.prototype = {
 			return true;
 
 		if (
-			!sv.popupMenuShown &&
+			!sv.isPopupShown() &&
 			(
 				!this.expanded ||
 				this.showHideReason & this.kKEEP_SHOWN_ON_MOUSEOVER
@@ -1125,7 +1140,9 @@ TreeStyleTabBrowserAutoHide.prototype = {
  
 	onResize : function TSTAutoHide_onResize(aEvent) 
 	{
+		var sv = this.mOwner;
 		if (
+			sv.isFloating ||
 			!aEvent.originalTarget ||
 			(
 				aEvent.originalTarget.ownerDocument != document &&
@@ -1135,7 +1152,6 @@ TreeStyleTabBrowserAutoHide.prototype = {
 			) {
 			return;
 		}
-		var sv = this.mOwner;
 		switch (sv.currentTabbarPosition)
 		{
 			case 'left':
diff --git a/modules/utils.js b/modules/utils.js
index 8e216a33..41d7414f 100644
--- a/modules/utils.js
+++ b/modules/utils.js
@@ -1881,8 +1881,8 @@ var TreeStyleTabUtils = {
 		if (expanded != originalExpanded ||
 			shrunken != originalShrunken) {
 			this.tabbarWidthResetting = true;
-			this.setTreePref('tabbar.width', expanded);
-			this.setTreePref('tabbar.shrunkenWidth', shrunken);
+			this.setTreePref('tabbar.width', Math.max(0, expanded));
+			this.setTreePref('tabbar.shrunkenWidth', Math.max(0, shrunken));
 			this.tabbarWidthResetting = false;
 		}
 	},
diff --git a/skin/classic/treestyletab/ui.css b/skin/classic/treestyletab/ui.css
index 6871f02c..3d684c80 100644
--- a/skin/classic/treestyletab/ui.css
+++ b/skin/classic/treestyletab/ui.css
@@ -120,7 +120,12 @@ tabbrowser[treestyletab-drop-position] {
 #TabsToolbar[treestyletab-drop-position="top"]:not([treestyletab-tabbar-position="top"]),
 #TabsToolbar[treestyletab-drop-position="right"]:not([treestyletab-tabbar-position="right"]),
 #TabsToolbar[treestyletab-drop-position="bottom"]:not([treestyletab-tabbar-position="bottom"]),
-#TabsToolbar[treestyletab-drop-position="left"]:not([treestyletab-tabbar-position="left"]) {
+#TabsToolbar[treestyletab-drop-position="left"]:not([treestyletab-tabbar-position="left"]),
+#TabsToolbar[treestyletab-drop-position="center"] #treestyletab-tabbar-resizer-box,
+#TabsToolbar[treestyletab-drop-position="top"]:not([treestyletab-tabbar-position="top"]) #treestyletab-tabbar-resizer-box,
+#TabsToolbar[treestyletab-drop-position="right"]:not([treestyletab-tabbar-position="right"]) #treestyletab-tabbar-resizer-box,
+#TabsToolbar[treestyletab-drop-position="bottom"]:not([treestyletab-tabbar-position="bottom"]) #treestyletab-tabbar-resizer-box,
+#TabsToolbar[treestyletab-drop-position="left"]:not([treestyletab-tabbar-position="left"]) #treestyletab-tabbar-resizer-box {
 	opacity: 0.5;
 }
 tabbrowser[treestyletab-drop-position="top"]:not([treestyletab-tabbar-position="top"]) {