diff --git a/content/treestyletab/res/stopRendering.js b/content/treestyletab/res/stopRendering.js
index 5c97b622..32b58095 100644
--- a/content/treestyletab/res/stopRendering.js
+++ b/content/treestyletab/res/stopRendering.js
@@ -12,7 +12,7 @@
    http://www.cozmixng.org/repos/piro/fx3-compatibility-lib/trunk/stopRendering.js
 */
 (function() {
-	const currentRevision = 1;
+	const currentRevision = 2;
 
 	if (!('piro.sakura.ne.jp' in window)) window['piro.sakura.ne.jp'] = {};
 
@@ -30,7 +30,7 @@
 
 		get rootContentViewer()
 		{
-			return window
+			return window.top
 					.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
 					.getInterface(Components.interfaces.nsIWebNavigation)
 					.QueryInterface(Components.interfaces.nsIDocShell)
@@ -38,18 +38,32 @@
 					.QueryInterface(Components.interfaces.nsIMarkupDocumentViewer);
 		},
 
+		get isActive()
+		{
+			return window.top.document.documentElement.getAttribute('active') == 'true';
+		},
+
 		stop : function()
 		{
-			if (!this._stopLevel)
+			if (!this._stopLevel) {
 				this.rootContentViewer.hide();
+			}
 			this._stopLevel++;
 		},
 
 		start : function()
 		{
 			this._stopLevel--;
-			if (!this._stopLevel)
+			if (!this._stopLevel) {
 				this.rootContentViewer.show();
+				if (this.isActive && !this.timer) {
+					this.timer = window.setTimeout(function(aSelf) {
+						aSelf.timer = null;
+						window.top.blur();
+						window.top.focus();
+					}, 0, this);
+				}
+			}
 		}
 
 	};