diff --git a/content/treestyletab/treestyletab.xul b/content/treestyletab/treestyletab.xul
index 7604f9fb..018ed4f4 100644
--- a/content/treestyletab/treestyletab.xul
+++ b/content/treestyletab/treestyletab.xul
@@ -14,12 +14,19 @@
 <script src="res/autoScroll.js" type="application/x-javascript; version=1.7"/>
 <script src="res/animationManager.js" type="application/x-javascript; version=1.7"/>
 <script src="res/extensions.js" type="application/x-javascript; version=1.7"/>
+
 <script src="treestyletab.js" type="application/x-javascript; version=1.7"/>
 <script src="treestyletabbrowser.js" type="application/x-javascript; version=1.7"/>
+<script src="treestyletabbrowser_tabbarDNDObserver.js" type="application/x-javascript; version=1.7"/>
+<script src="treestyletabbrowser_tabpanelDNDObserver.js" type="application/x-javascript; version=1.7"/>
+
 <script src="preloadImages.js" type="application/x-javascript; version=1.7"/>
+
 <script src="bookmarksOverlay.js" type="application/x-javascript; version=1.7"/>
 <script src="bookmarksOverlayEditable.js" type="application/x-javascript; version=1.7"/>
+
 <script src="hacks.js" type="application/x-javascript; version=1.7"/>
+
 <script type="application/x-javascript; version=1.7"><![CDATA[
 	// preload images
 	TreeStyleTabService.observe(
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 81792b8d..a1768e79 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -2347,242 +2347,19 @@ TreeStyleTabBrowser.prototype = {
 	},
    
 /* drag and drop */ 
-	autoExpandTimer  : null,
-	autoExpandTarget : null,
-	autoExpandedTabs : [],
 	
-	// tabbar 
-	get tabbarDNDObserver()
+	get tabbarDNDObserver() 
 	{
-		if (!this._tabbarDNDObserver)
-			this._tabbarDNDObserver = {
-				mOwner : this,
-	
-	onDragStart : function(aEvent, aTransferData, aDragAction) 
-	{
-		if (!this.canDragTabbar(aEvent))
-			return false;
-
-		var sv = this.mOwner;
-		aTransferData.data = new TransferData();
-		aTransferData.data.addDataForFlavour(
-			sv.kDRAG_TYPE_TABBAR,
-			aEvent.shiftKey ?
-				sv.kTABBAR_MOVE_FORCE :
-				sv.kTABBAR_MOVE_NORMAL
-		);
-		sv.mTabBrowser.setAttribute(sv.kDROP_POSITION, sv.kDROP_POSITION_UNKNOWN);
-
-		aEvent.stopPropagation();
-		return true;
+		delete this.tabbarDNDObserver;
+		return (this.tabbarDNDObserver = new TreeStyleTabBrowserTabbarDNDObserver(this));
 	},
  
-	canDragTabbar : function(aEvent) 
+	get panelDNDObserver() 
 	{
-		var sv = this.mOwner;
-		var tab = sv.getTabFromEvent(aEvent);
-		var tabbar = sv.getTabbarFromEvent(aEvent);
-		return (
-				(tab ? aEvent.shiftKey : tabbar ) &&
-				(
-					aEvent.shiftKey ||
-					sv.mTabBrowser.getAttribute(sv.kFIXED) != 'true'
-				)
-			);
+		delete this.panelDNDObserver;
+		return (this.panelDNDObserver = new TreeStyleTabBrowserTabpanelDNDObserver(this));
 	},
  
-	onDragEnter : function(aEvent, aDragSession) 
-	{
-		var sv = this.mOwner;
-		var tab = aEvent.target;
-		if (tab.localName != 'tab' ||
-			!sv.getTreePref('autoExpand.enabled'))
-			return;
-
-		var now = (new Date()).getTime();
-
-		window.clearTimeout(sv.autoExpandTimer);
-		if (aEvent.target == aDragSession.sourceNode) return;
-		sv.autoExpandTimer = window.setTimeout(
-			function(aTarget) {
-				let tab = sv.getTabById(aTarget);
-				if (tab &&
-					tab.getAttribute(sv.kSUBTREE_COLLAPSED) == 'true' &&
-					tab.getAttribute(sv.kDROP_POSITION) == 'self') {
-					if (sv.getTreePref('autoExpand.intelligently')) {
-						sv.collapseExpandTreesIntelligentlyFor(tab);
-					}
-					else {
-						sv.autoExpandedTabs.push(aTarget);
-						sv.collapseExpandSubtree(tab, false);
-					}
-				}
-			},
-			sv.getTreePref('autoExpand.delay'),
-			tab.getAttribute(sv.kID)
-		);
-
-		tab = null;
-		now = null;
-	},
- 
-	onDragExit : function(aEvent, aDragSession) 
-	{
-		var sv = this.mOwner;
-		var now = (new Date()).getTime();
-
-		window.clearTimeout(sv.autoExpandTimer);
-		sv.autoExpandTimer = null;
-	},
- 
-	onDragEnd : function(aEvent) 
-	{
-		var sv = this.mOwner;
-		window.setTimeout(function() {
-			sv.mTabBrowser.removeAttribute(sv.kDROP_POSITION);
-		}, 10);
-		aEvent.stopPropagation();
-	},
- 
-	onDragOver : function(aEvent, aFlavour, aDragSession) 
-	{
-	},
- 
-	onDrop : function(aEvent, aXferData, aDragSession) 
-	{
-		var sv = this.mOwner;
-		if (!sv.autoExpandedTabs.length) return;
-		if (sv.getTreePref('autoExpand.collapseFinally')) {
-			sv.autoExpandedTabs.forEach(function(aTarget) {
-				this.collapseExpandSubtree(this.getTabById(aTarget), true, true);
-			}, sv);
-		}
-		sv.autoExpandedTabs = [];
-	},
- 
-	canDrop : function(aEvent, aDragSession) 
-	{
-		var sv = this.mOwner;
-		var tooltip = sv.mTabBrowser.mStrip.firstChild;
-		if (tooltip &&
-			tooltip.localName == 'tooltip' &&
-			tooltip.popupBoxObject.popupState != 'closed')
-			tooltip.hidePopup();
-
-		var dropAction = sv.getDropAction(aEvent, aDragSession);
-		if ('dataTransfer' in aEvent) {
-			var dt = aEvent.dataTransfer;
-			if (dropAction.action & this.kACTION_NEWTAB) {
-				dt.effectAllowed = dt.dropEffect = (
-					!dropAction.source ? 'link' :
-					sv.isAccelKeyPressed(aEvent) ? 'copy' :
-					'move'
-				);
-			}
-		}
-		return dropAction.canDrop;
-	},
- 
-	getSupportedFlavours : function() 
-	{
-		var flavourSet = new FlavourSet();
-		flavourSet.appendFlavour('application/x-moz-tabbrowser-tab');
-		flavourSet.appendFlavour('text/x-moz-url');
-		flavourSet.appendFlavour('text/unicode');
-		flavourSet.appendFlavour('text/plain');
-		flavourSet.appendFlavour('application/x-moz-file', 'nsIFile');
-		return flavourSet;
-	}
- 
-			};
-		return this._tabbarDNDObserver;
-	}, 
-  
-	// content area 
-	get panelDNDObserver()
-	{
-		if (!this._panelDNDObserver)
-			this._panelDNDObserver = {
-				mOwner : this,
-	
-	onDragExit : function(aEvent, aDragSession) 
-	{
-		if (!this.canDrop(aEvent, aDragSession)) return;
-		var sv = this.mOwner;
-		sv.mTabBrowser.setAttribute(sv.kDROP_POSITION, sv.kDROP_POSITION_UNKNOWN);
-	},
- 
-	onDragOver : function(aEvent, aFlavour, aDragSession) 
-	{
-		if (!this.canDrop(aEvent, aDragSession)) return;
-		var sv = this.mOwner;
-		var position = this.getDropPosition(aEvent);
-		if (position != 'center' &&
-			position != sv.mTabBrowser.getAttribute(sv.kTABBAR_POSITION))
-			sv.mTabBrowser.setAttribute(sv.kDROP_POSITION, position);
-	},
- 
-	onDrop : function(aEvent, aXferData, aDragSession) 
-	{
-		var sv = this.mOwner;
-		var position = this.getDropPosition(aEvent);
-		if (position != 'center' &&
-			position != sv.mTabBrowser.getAttribute(sv.kTABBAR_POSITION)) {
-			if (sv.getTreePref('tabbar.fixed.autoCancelOnDrop') &&
-				aXferData.data != sv.kTABBAR_MOVE_FORCE) {
-				let orient = (position == 'left' || position == 'right') ? 'vertical' : 'horizontal' ;
-				sv.setTreePref('tabbar.fixed.'+orient, false);
-			}
-			sv.changeTabbarPosition(position);
-		}
-
-		aEvent.stopPropagation();
-	},
- 
-	getDropPosition : function(aEvent) 
-	{
-		var box = this.mOwner.mTabBrowser.boxObject;
-		var W = box.width;
-		var H = box.height;
-		var X = box.screenX;
-		var Y = box.screenY;
-		var x = aEvent.screenX - X;
-		var y = aEvent.screenY - Y;
-
-		if (x > (W * 0.33) &&
-			x < (W * 0.66) &&
-			y > (H * 0.33) &&
-			y < (H * 0.66))
-			return 'center';
-
-		var isTL = x <= W - (y * W / H);
-		var isBL = x <= y * W / H;
-		return (isTL && isBL) ? 'left' :
-				(isTL && !isBL) ? 'top' :
-				(!isTL && isBL) ? 'bottom' :
-				'right' ;
-	},
- 
-	canDrop : function(aEvent, aDragSession) 
-	{
-		return (
-				aDragSession &&
-				aDragSession.isDataFlavorSupported(this.mOwner.kDRAG_TYPE_TABBAR) &&
-				aDragSession.sourceNode
-			) ? true : false ;
-	},
- 
-	getSupportedFlavours : function() 
-	{
-		var flavourSet = new FlavourSet();
-		flavourSet.appendFlavour(this.mOwner.kDRAG_TYPE_TABBAR);
-		return flavourSet;
-	}
- 
-			};
-		return this._panelDNDObserver;
-	}, 
-  
 	getCurrentDragSession : function() 
 	{
 		return Components
diff --git a/content/treestyletab/treestyletabbrowser_tabbarDNDObserver.js b/content/treestyletab/treestyletabbrowser_tabbarDNDObserver.js
new file mode 100644
index 00000000..6a942794
--- /dev/null
+++ b/content/treestyletab/treestyletabbrowser_tabbarDNDObserver.js
@@ -0,0 +1,147 @@
+function TreeStyleTabBrowserTabbarDNDObserver(aOwner) 
+{
+	this.mOwner = aOwner;
+	this.mAutoExpandTimer = null;
+	this.mAutoExpandedTabs = [],
+}
+
+TreeStyleTabBrowserTabbarDNDObserver.prototype = {
+	 
+	onDragStart : function(aEvent, aTransferData, aDragAction) 
+	{
+		if (!this.canDragTabbar(aEvent))
+			return false;
+
+		var sv = this.mOwner;
+		aTransferData.data = new TransferData();
+		aTransferData.data.addDataForFlavour(
+			sv.kDRAG_TYPE_TABBAR,
+			aEvent.shiftKey ?
+				sv.kTABBAR_MOVE_FORCE :
+				sv.kTABBAR_MOVE_NORMAL
+		);
+		sv.mTabBrowser.setAttribute(sv.kDROP_POSITION, sv.kDROP_POSITION_UNKNOWN);
+
+		aEvent.stopPropagation();
+		return true;
+	},
+ 
+	canDragTabbar : function(aEvent) 
+	{
+		var sv = this.mOwner;
+		var tab = sv.getTabFromEvent(aEvent);
+		var tabbar = sv.getTabbarFromEvent(aEvent);
+		return (
+				(tab ? aEvent.shiftKey : tabbar ) &&
+				(
+					aEvent.shiftKey ||
+					sv.mTabBrowser.getAttribute(sv.kFIXED) != 'true'
+				)
+			);
+	},
+ 
+	onDragEnter : function(aEvent, aDragSession) 
+	{
+		var sv = this.mOwner;
+		var tab = aEvent.target;
+		if (tab.localName != 'tab' ||
+			!sv.getTreePref('autoExpand.enabled'))
+			return;
+
+		var now = (new Date()).getTime();
+
+		window.clearTimeout(this.mAutoExpandTimer);
+		if (aEvent.target == aDragSession.sourceNode) return;
+		this.mAutoExpandTimer = window.setTimeout(
+			function(aTarget) {
+				let tab = sv.getTabById(aTarget);
+				if (tab &&
+					tab.getAttribute(sv.kSUBTREE_COLLAPSED) == 'true' &&
+					tab.getAttribute(sv.kDROP_POSITION) == 'self') {
+					if (sv.getTreePref('autoExpand.intelligently')) {
+						sv.collapseExpandTreesIntelligentlyFor(tab);
+					}
+					else {
+						this.mAutoExpandedTabs.push(aTarget);
+						sv.collapseExpandSubtree(tab, false);
+					}
+				}
+			},
+			sv.getTreePref('autoExpand.delay'),
+			tab.getAttribute(sv.kID)
+		);
+
+		tab = null;
+		now = null;
+	},
+ 
+	onDragExit : function(aEvent, aDragSession) 
+	{
+		var sv = this.mOwner;
+		var now = (new Date()).getTime();
+
+		window.clearTimeout(this.mAutoExpandTimer);
+		this.mAutoExpandTimer = null;
+	},
+ 
+	onDragEnd : function(aEvent) 
+	{
+		var sv = this.mOwner;
+		window.setTimeout(function() {
+			sv.mTabBrowser.removeAttribute(sv.kDROP_POSITION);
+		}, 10);
+		aEvent.stopPropagation();
+	},
+ 
+	onDragOver : function(aEvent, aFlavour, aDragSession) 
+	{
+	},
+ 
+	onDrop : function(aEvent, aXferData, aDragSession) 
+	{
+		var sv = this.mOwner;
+		if (!this.mAutoExpandedTabs.length) return;
+		if (sv.getTreePref('autoExpand.collapseFinally')) {
+			this.mAutoExpandedTabs.forEach(function(aTarget) {
+				this.collapseExpandSubtree(this.getTabById(aTarget), true, true);
+			}, sv);
+		}
+		this.mAutoExpandedTabs = [];
+	},
+ 
+	canDrop : function(aEvent, aDragSession) 
+	{
+		var sv = this.mOwner;
+		var tooltip = sv.mTabBrowser.mStrip.firstChild;
+		if (tooltip &&
+			tooltip.localName == 'tooltip' &&
+			tooltip.popupBoxObject.popupState != 'closed')
+			tooltip.hidePopup();
+
+		var dropAction = sv.getDropAction(aEvent, aDragSession);
+		if ('dataTransfer' in aEvent) {
+			var dt = aEvent.dataTransfer;
+			if (dropAction.action & this.kACTION_NEWTAB) {
+				dt.effectAllowed = dt.dropEffect = (
+					!dropAction.source ? 'link' :
+					sv.isAccelKeyPressed(aEvent) ? 'copy' :
+					'move'
+				);
+			}
+		}
+		return dropAction.canDrop;
+	},
+ 
+	getSupportedFlavours : function() 
+	{
+		var flavourSet = new FlavourSet();
+		flavourSet.appendFlavour('application/x-moz-tabbrowser-tab');
+		flavourSet.appendFlavour('text/x-moz-url');
+		flavourSet.appendFlavour('text/unicode');
+		flavourSet.appendFlavour('text/plain');
+		flavourSet.appendFlavour('application/x-moz-file', 'nsIFile');
+		return flavourSet;
+	}
+ 
+}; 
+  
diff --git a/content/treestyletab/treestyletabbrowser_tabpanelDNDObserver.js b/content/treestyletab/treestyletabbrowser_tabpanelDNDObserver.js
new file mode 100644
index 00000000..fd14a0d2
--- /dev/null
+++ b/content/treestyletab/treestyletabbrowser_tabpanelDNDObserver.js
@@ -0,0 +1,83 @@
+function TreeStyleTabBrowserTabpanelDNDObserver(aOwner) 
+{
+	this.mOwner = aOwner;
+}
+
+TreeStyleTabBrowserTabpanelDNDObserver.prototype = {
+	 
+	onDragExit : function(aEvent, aDragSession) 
+	{
+		if (!this.canDrop(aEvent, aDragSession)) return;
+		var sv = this.mOwner;
+		sv.mTabBrowser.setAttribute(sv.kDROP_POSITION, sv.kDROP_POSITION_UNKNOWN);
+	},
+ 
+	onDragOver : function(aEvent, aFlavour, aDragSession) 
+	{
+		if (!this.canDrop(aEvent, aDragSession)) return;
+		var sv = this.mOwner;
+		var position = this.getDropPosition(aEvent);
+		if (position != 'center' &&
+			position != sv.mTabBrowser.getAttribute(sv.kTABBAR_POSITION))
+			sv.mTabBrowser.setAttribute(sv.kDROP_POSITION, position);
+	},
+ 
+	onDrop : function(aEvent, aXferData, aDragSession) 
+	{
+		var sv = this.mOwner;
+		var position = this.getDropPosition(aEvent);
+		if (position != 'center' &&
+			position != sv.mTabBrowser.getAttribute(sv.kTABBAR_POSITION)) {
+			if (sv.getTreePref('tabbar.fixed.autoCancelOnDrop') &&
+				aXferData.data != sv.kTABBAR_MOVE_FORCE) {
+				let orient = (position == 'left' || position == 'right') ? 'vertical' : 'horizontal' ;
+				sv.setTreePref('tabbar.fixed.'+orient, false);
+			}
+			sv.changeTabbarPosition(position);
+		}
+
+		aEvent.stopPropagation();
+	},
+ 
+	getDropPosition : function(aEvent) 
+	{
+		var box = this.mOwner.mTabBrowser.boxObject;
+		var W = box.width;
+		var H = box.height;
+		var X = box.screenX;
+		var Y = box.screenY;
+		var x = aEvent.screenX - X;
+		var y = aEvent.screenY - Y;
+
+		if (x > (W * 0.33) &&
+			x < (W * 0.66) &&
+			y > (H * 0.33) &&
+			y < (H * 0.66))
+			return 'center';
+
+		var isTL = x <= W - (y * W / H);
+		var isBL = x <= y * W / H;
+		return (isTL && isBL) ? 'left' :
+				(isTL && !isBL) ? 'top' :
+				(!isTL && isBL) ? 'bottom' :
+				'right' ;
+	},
+ 
+	canDrop : function(aEvent, aDragSession) 
+	{
+		return (
+				aDragSession &&
+				aDragSession.isDataFlavorSupported(this.mOwner.kDRAG_TYPE_TABBAR) &&
+				aDragSession.sourceNode
+			) ? true : false ;
+	},
+ 
+	getSupportedFlavours : function() 
+	{
+		var flavourSet = new FlavourSet();
+		flavourSet.appendFlavour(this.mOwner.kDRAG_TYPE_TABBAR);
+		return flavourSet;
+	}
+ 
+}; 
+