diff --git a/data/inject.js b/data/inject.js
index 8056e68..dd09aec 100644
--- a/data/inject.js
+++ b/data/inject.js
@@ -1,40 +1,82 @@
-var getContext = unsafeWindow.HTMLCanvasElement.prototype.getContext;
-var askFunctionName = Math.random().toString(16);
+(function(){
+	"use strict";
+	
+	var getContext = unsafeWindow.HTMLCanvasElement.prototype.getContext;
+	var askFunctionName = Math.random().toString(16);
 
-function checkPDF(blocking){
-	if (unsafeWindow.document.contentType.match(/\/pdf$/i)){
-		self.port.emit("isPDF", blocking);
-		return true;
+	function checkPDF(blocking){
+		if (document.contentType.match(/\/pdf$/i)){
+			self.port.emit("isPDF", blocking);
+			return true;
+		}
+		return false;
 	}
-	return false;
-}
 
-function block(force){
-	if (force || !checkPDF("block")){
-		// consoe.log("block");
-		delete unsafeWindow.HTMLCanvasElement.prototype[askFunctionName];
-		unsafeWindow.HTMLCanvasElement.prototype.getContext = null;
+	function block(force){
+		if (force || !checkPDF("block")){
+			// consoe.log("block");
+			delete unsafeWindow.HTMLCanvasElement.prototype[askFunctionName];
+			unsafeWindow.HTMLCanvasElement.prototype.getContext = null;
+		}
 	}
-}
 
-function ask(force){
-	if (force || !checkPDF("ask")){
-		// console.log("ask");
-		
-		Object.defineProperty(
-			unsafeWindow.HTMLCanvasElement.prototype,
-			askFunctionName,
-			{
-				value: getContext,
-				enumerabe: false
-			}
-		);
-		unsafeWindow.HTMLCanvasElement.prototype.getContext = new unsafeWindow.Function(
-			function(){
-				if (this.parentNode){
+	function askVisible(force){
+		if (force || !checkPDF("askVisible")){
+			
+			Object.defineProperty(
+				unsafeWindow.HTMLCanvasElement.prototype,
+				askFunctionName,
+				{
+					value: getContext,
+					enumerabe: false
+				}
+			);
+			unsafeWindow.HTMLCanvasElement.prototype.getContext = new unsafeWindow.Function(
+				function(){
+					if (this.parentNode){
+						var oldBorder = this.style.border;
+						this.style.border = "2px dashed red";
+						var confirmText = "askForPermission";
+						var allow = confirm(confirmText);
+						this.style.border = oldBorder;
+						if (allow){
+							this.getContext = this["askFunctionName"];
+							return this["askFunctionName"].apply(this, arguments);
+						}
+						else {
+							this.getContext = null;
+							return null;
+						}
+					}
+					else {
+						return null;
+					}
+				}.toString()
+					.replace(/^function\s*\(\)\s*\{|\}\s*$/g, "")
+					.replace(/askFunctionName/g, askFunctionName)
+					.replace(/askForPermission/g, _("askForPermission"))
+			);
+		}
+	}
+	function askInvisible(force){
+		if (force || !checkPDF("askInvisible")){
+			
+			Object.defineProperty(
+				unsafeWindow.HTMLCanvasElement.prototype,
+				askFunctionName,
+				{
+					value: getContext,
+					enumerabe: false
+				}
+			);
+			unsafeWindow.HTMLCanvasElement.prototype.getContext = new unsafeWindow.Function(
+				function(){
 					var oldBorder = this.style.border;
 					this.style.border = "2px dashed red";
-					var confirmText = "askForPermission";
+					var confirmText =
+						this.parentNode?
+						"askForPermission":
+						"askForInvisiblePermission";
 					var allow = confirm(confirmText);
 					this.style.border = oldBorder;
 					if (allow){
@@ -45,70 +87,30 @@ function ask(force){
 						this.getContext = null;
 						return null;
 					}
-				}
-				else {
-					return null;
-				}
-			}.toString()
-				.replace(/^function\s*\(\)\s*\{|\}\s*$/g, "")
-				.replace(/askFunctionName/g, askFunctionName)
-				.replace(/askForPermission/g, _("askForPermission"))
-		);
+				}.toString()
+					.replace(/^function\s*\(\)\s*\{|\}\s*$/g, "")
+					.replace(/askFunctionName/g, askFunctionName)
+					.replace(/askForPermission/g, _("askForPermission"))
+					.replace(/askForInvisiblePermission/g, _("askForInvisiblePermission"))
+			);
+		}
 	}
-}
-function askInvisible(force){
-	if (force || !checkPDF("askInvisible")){
-		// console.log("ask");
-		
-		Object.defineProperty(
-			unsafeWindow.HTMLCanvasElement.prototype,
-			askFunctionName,
-			{
-				value: getContext,
-				enumerabe: false
-			}
-		);
-		unsafeWindow.HTMLCanvasElement.prototype.getContext = new unsafeWindow.Function(
-			function(){
-				var oldBorder = this.style.border;
-				this.style.border = "2px dashed red";
-				var confirmText =
-					this.parentNode?
-					"askForPermission":
-					"askForInvisiblePermission";
-				var allow = confirm(confirmText);
-				this.style.border = oldBorder;
-				if (allow){
-					this.getContext = this["askFunctionName"];
-					return this["askFunctionName"].apply(this, arguments);
-				}
-				else {
-					this.getContext = null;
-					return null;
-				}
-			}.toString()
-				.replace(/^function\s*\(\)\s*\{|\}\s*$/g, "")
-				.replace(/askFunctionName/g, askFunctionName)
-				.replace(/askForPermission/g, _("askForPermission"))
-				.replace(/askForInvisiblePermission/g, _("askForInvisiblePermission"))
-		);
+	function unblock(){
+		// console.log("unblock");
+		unsafeWindow.HTMLCanvasElement.prototype.getContext = getContext;
 	}
-}
-function unblock(){
-	// console.log("unblock");
-	unsafeWindow.HTMLCanvasElement.prototype.getContext = getContext;
-}
 
-var _ = function(name){
-	return _[name] || name;
-}
-self.port.on("setTranslation", function(name, translation){
-	_[name] = translation;
-});
+	var _ = function(name){
+		return _[name] || name;
+	}
+	self.port.on("setTranslation", function(name, translation){
+		_[name] = translation;
+	});
 
-block();
-self.port.on("block", block);
-self.port.on("ask", ask);
-self.port.on("askInvisible", askInvisible);
-self.port.on("unblock", unblock);
-self.port.on("detach", unblock);
\ No newline at end of file
+	block();
+	self.port.on("block", block);
+	self.port.on("askVisible", askVisible);
+	self.port.on("askInvisible", askInvisible);
+	self.port.on("unblock", unblock);
+	self.port.on("detach", unblock);
+}());
\ No newline at end of file
diff --git a/lib/main.js b/lib/main.js
index a946fe5..c985a74 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -1,157 +1,162 @@
-function getDomainRegExpList(domainList){
-	return domainList
-		.split(",")
-		.map(function(entry){
-			return entry.replace(/^\s+|\s+$/g, "");
-		})
-		.filter(function(entry){
-			return !!entry.length;
-		})
-		.map(function(entry){
-			var regExp;
-			var domain = !!entry.match(/^[\w.]+$/);
-			if (domain){
-				regExp = new RegExp("(?:^|\\.)" + entry.replace(/([\\\+\*\?\[\^\]\$\(\)\{\}\=\!\|\.])/g, "\\$1") + "\\.?$", "i")
-			}
-			else {
-				regExp = new RegExp(entry, "i");
-			}
-			return {
-				match: function(url){
-					if (domain){
-						return url.hostname.match(regExp);
-					}
-					else {
-						return url.href.match(regExp);
-					}
+(function(){
+"use strict";
+
+	function getDomainRegExpList(domainList){
+		var list = domainList
+			.split(",")
+			.map(function(entry){
+				return entry.replace(/^\s+|\s+$/g, "");
+			})
+			.filter(function(entry){
+				return !!entry.length;
+			})
+			.map(function(entry){
+				var regExp;
+				var domain = !!entry.match(/^[\w.]+$/);
+				if (domain){
+					regExp = new RegExp("(?:^|\\.)" + entry.replace(/([\\\+\*\?\[\^\]\$\(\)\{\}\=\!\|\.])/g, "\\$1") + "\\.?$", "i")
 				}
-			};
-		});
-}
-
-var self = require("sdk/self");
-var pageMod = require("sdk/page-mod");
-var preferences = require("sdk/simple-prefs");
-var prefs = preferences.prefs;
-var {URL} = require("sdk/url");
-var _ = require("sdk/l10n").get;
-
-// preferences
-var whiteList;
-function updateWhiteList(){
-	whiteList = getDomainRegExpList(prefs.whiteList);
-}
-updateWhiteList();
-preferences.on("whiteList", function(){
-	updateWhiteList();
-	workers.forEach(checkWorker);
-});
-
-var blackList;
-function updateBlackList(){
-	blackList = getDomainRegExpList(prefs.blackList);
-}
-updateBlackList();
-preferences.on("blackList", function(){
-	updateBlackList();
-	workers.forEach(checkWorker);
-});
-
-
-var workers = [];
-function detachWorker(worker, workerArray) {
-	var index = workerArray.indexOf(worker);
-	if (index != -1){
-		workerArray.splice(index, 1);
-	}
-}
-function checkWorker(worker){
-	if (prefs.blockAll){
-		worker.port.emit("block");
-	}
-	else {
-		var url = new URL(worker.url);
-		var inBlackList = blackList.some(function(entry){
-			return entry.match(url);
-		});
-		if (inBlackList){
-			worker.port.emit("block");
-		}
-		else {
-			var inWhiteList = whiteList.some(function(entry){
-				return entry.match(url);
+				else {
+					regExp = new RegExp(entry, "i");
+				}
+				return {
+					match: function(url){
+						if (domain){
+							return url.hostname.match(regExp);
+						}
+						else {
+							return url.href.match(regExp);
+						}
+					}
+				};
 			});
-			if (inWhiteList){
-				worker.port.emit("unblock");
+			
+			list.match = function(url){
+				return this.some(function(entry){
+					return entry.match(url);
+				})
 			}
-			else {
-				if (prefs.askPermission){
-					if (prefs.askInvisiblePermission){
-						worker.port.emit("askInvisible");
-					}
-					else {
-						worker.port.emit("ask");
-					}
+			
+			return list;
+	}
+
+	var self = require("sdk/self");
+	var pageMod = require("sdk/page-mod");
+	var preferences = require("sdk/simple-prefs");
+	var prefs = preferences.prefs;
+	var {URL} = require("sdk/url");
+	var _ = require("sdk/l10n").get;
+
+	// preferences
+	var whiteList;
+	function updateWhiteList(){
+		whiteList = getDomainRegExpList(prefs.whiteList);
+	}
+	updateWhiteList();
+	preferences.on("whiteList", function(){
+		updateWhiteList();
+		workers.forEach(checkWorker);
+	});
+
+	var blackList;
+	function updateBlackList(){
+		blackList = getDomainRegExpList(prefs.blackList);
+	}
+	updateBlackList();
+	preferences.on("blackList", function(){
+		updateBlackList();
+		workers.forEach(checkWorker);
+	});
+	
+	
+	preferences.on("blockMode", function(){
+		workers.forEach(checkWorker);
+	});preferences.on("allowPDFCanvas", function(){
+		workers.forEach(checkWorker);
+	});
+
+	var workers = [];
+	function detachWorker(worker, workerArray) {
+		var index = workerArray.indexOf(worker);
+		if (index != -1){
+			workerArray.splice(index, 1);
+		}
+	}
+	function checkWorker(worker){
+		var url = new URL(worker.url);
+		switch (prefs.blockMode){
+			case "blockEverything":
+				worker.port.emit("block");
+				break;
+			case "allowOnlyWhiteList":
+				if (whiteList.match(url)){
+					worker.port.emit("unblock");
 				}
 				else {
 					worker.port.emit("block");
 				}
-			}
+				break;
+			case "askVisible":
+				if (whiteList.match(url)){
+					worker.port.emit("unblock");
+				}
+				else if (blackList.match(url)){
+					worker.port.emit("block");
+				}
+				else {
+					worker.port.emit("askVisible");
+				}
+				break;
+			case "askInvisible":
+				if (whiteList.match(url)){
+					worker.port.emit("unblock");
+				}
+				else if (blackList.match(url)){
+					worker.port.emit("block");
+				}
+				else {
+					worker.port.emit("askInvisible");
+				}
+				break;
+			case "blockOnlyBlackList":
+				if (blackList.match(url)){
+					worker.port.emit("block");
+				}
+				else {
+					worker.port.emit("unblock");
+				}
+				break;
+			case "allowEverything":
+				worker.port.emit("unblock");
+				break;
+			default:
+				console.log("Unknown blocking mode.");
 		}
 	}
-}
-
-preferences.on("blockAll", function(){
-	if (prefs.blockAll){
-		prefs.askPermission = false;
-		prefs.askInsiviblePermission = false;
-	}
-	workers.forEach(checkWorker);
-});
-preferences.on("askPermission", function(){
-	if (prefs.askPermission){
-		prefs.blockAll = false;
-	}
-	else {
-		prefs.askInvisiblePermission = false;
-	}
-	workers.forEach(checkWorker);
-});
-preferences.on("askInvisiblePermission", function(){
-	if (prefs.askInvisiblePermission){
-		prefs.askPermission = true;
-		prefs.blockAll = false;
-	}
-	workers.forEach(checkWorker);
-});
-preferences.on("allowPDFCanvas", function(){
-	workers.forEach(checkWorker);
-});
 
 
-pageMod.PageMod({
-	include: "*",
-	contentScriptWhen: "start",
-	contentScriptFile: self.data.url("inject.js"),
-	onAttach: function(worker){
-		
-		workers.push(worker);
-		worker.on("detach", function(){
-			detachWorker(this, workers);
-		});
-		worker.port.on("getTranslation", function(name){
-			worker.port.emit("setTranslation", name, _.apply(null, arguments));
-		});
-		worker.port.on("isPDF", function(blocking){
-			if (prefs.allowPDFCanvas){
-				worker.port.emit("unblock");
-			}
-			else {
-				worker.port.emit(blocking, true);
-			}
-		});
-		worker.port.emit("setTranslation", "askForPermission", _("askForPermission"));
-		worker.port.emit("setTranslation", "askForInvisiblePermission", _("askForInvisiblePermission"));
-		checkWorker(worker);
-	},
-});
\ No newline at end of file
+	pageMod.PageMod({
+		include: "*",
+		contentScriptWhen: "start",
+		contentScriptFile: self.data.url("inject.js"),
+		onAttach: function(worker){
+			
+			workers.push(worker);
+			worker.on("detach", function(){
+				detachWorker(this, workers);
+			});
+			worker.port.on("isPDF", function(blocking){
+				if (prefs.allowPDFCanvas){
+					worker.port.emit("unblock");
+				}
+				else {
+					worker.port.emit(blocking, true);
+				}
+			});
+			worker.port.emit("setTranslation", "askForPermission", _("askForPermission"));
+			worker.port.emit("setTranslation", "askForInvisiblePermission", _("askForInvisiblePermission"));
+			checkWorker(worker);
+		},
+	});
+
+}());
\ No newline at end of file
diff --git a/locale/de-DE.properties b/locale/de-DE.properties
index 377dacb..423830a 100644
--- a/locale/de-DE.properties
+++ b/locale/de-DE.properties
@@ -1,17 +1,18 @@
 whilteList_title= Whitelist
 whiteList_description= Domänen oder URLs, die die <canvas>-API verwenden dürfen. Mehrere Einträge müssen durch ein Komma getrennt weren.
 
-blockAll_title= Alles blockieren
-blockAll_description= Ob immer alles blockiert werden soll (ignoriert die Whitelist).
-
 blackList_title= Blacklist
 blackList_description= Domänen oder URLs, die die <canvas>-API niemals verwenden dürfen. Mehrere Einträge müssen durch ein Komma getrennt weren.
 
-askPermission_title= Um Erlaubnis fragen
-askPermission_description= Ob man gefragt werden soll, ob ein sichtbares <canvas>-Element blockiert werden soll oder nicht, wenn die Domäne oder URL weder auf der Whitelist noch auf der Blacklist steht.
+blockMode_title= Blockiermodus
+blockMode_description=
 
-askInvisiblePermission_title= Bei verstecken Elementen um Erlaubnis fragen
-askInvisiblePermission_description= Ob man gefragt werden soll, ob ein verstecktes <canvas>-Element blockiert werden soll oder nicht, wenn die Domäne oder URL weder auf der Whitelist noch auf der Blacklist steht.
+blockMode_options.block everything= alles blockieren
+blockMode_options.allow only white list= nur Einträge der Whitelist erlauben
+blockMode_options.ask for permission for visible <canvas>= bei sichtbaren <canvas> um Erlaubnis fragen
+blockMode_options.ask for permision for invisible <canvas>= bei unsichtbaren <canvas> um Erlaubnis fragen
+blockMode_options.block only black list= nur Einträge der Blacklist blockieren
+blockMode_options.allow everything= alles erlauben
 
 allowPDFCanvas_title= <canvas> in PDFs erlauben
 allowPDFCanvas_description= Die native pdf.js verwendet <canvas> um den Inhalt von PDFs anzuzeigen. Wenn dies nicht markiert ist, werden viele Nachfragedialoge erscheinen oder die PDF Ansicht nicht funktionieren.
diff --git a/locale/en-US.properties b/locale/en-US.properties
index c876eb0..ba574d5 100644
--- a/locale/en-US.properties
+++ b/locale/en-US.properties
@@ -1,17 +1,18 @@
 whilteList_title= White list
 whiteList_description= Domains or URLs where the <canvas>-API should not be blocked. To add multiple entries seperate them by comma.
 
-blockAll_title= Block everything
-blockAll_description= If you want to block everything (ignore the white list).
-
 blackList_title= Black list
 blackList_description= Domains or URLs where the <canvas>-API should always be blocked. To add multiple entries seperate them by comma.
 
-askPermission_title= Ask for permission
-askPermission_description= If you want to be asked if you want to block a visible canvas element if the domain or URL is neither in the white or black list.
+blockMode_title= Block mode
+blockMode_description=
 
-askInvisiblePermission_title= Ask for permission for invisible elements
-askInvisiblePermission_description= If you want to be asked if you want to block an invisible canvas element if the domain or URL is neither in the white or black list.
+blockMode_options.block everything= block everything
+blockMode_options.allow only white list= allow only white list
+blockMode_options.ask for permission for visible <canvas>= ask for permission for visible <canvas>
+blockMode_options.ask for permision for invisible <canvas>= ask for permision for invisible <canvas>
+blockMode_options.block only black list= block only black list
+blockMode_options.allow everything= allow everything
 
 allowPDFCanvas_title= Allow canvas in PDFs
 allowPDFCanvas_description= The native pdf.js uses <canvas> to display the PDF content. If this is unchecked there will lots of annoying ask dialogs or the PDF display will not work.
diff --git a/package.json b/package.json
index bab5f49..8911a93 100644
--- a/package.json
+++ b/package.json
@@ -10,12 +10,6 @@
 			"type": "string",
 			"value": "kkapsner.de,^https?://(\\\\w+\\\\.)*google.[a-z]+/maps"
 		},
-		{
-			"name": "blockAll",
-			"title": "Block everything",
-			"type": "bool",
-			"value": false
-		},
 		{
 			"name": "blackList",
 			"title": "Black list",
@@ -23,16 +17,36 @@
 			"value": ""
 		},
 		{
-			"name": "askPermission",
-			"title": "Ask for permission",
-			"type": "bool",
-			"value": true
-		},
-		{
-			"name": "askInvisiblePermission",
-			"title": "Ask for permission for invisible elements",
-			"type": "bool",
-			"value": false
+			"name": "blockMode",
+			"title": "block mode",
+			"type": "menulist",
+			"value": "askVisible",
+			"options": [
+				{
+					"value": "blockEverything",
+					"label": "block everything"
+				},
+				{
+					"value": "allowOnlyWhiteList",
+					"label": "allow only white list"
+				},
+				{
+					"value": "askVisible",
+					"label": "ask for permission for visible <canvas>"
+				},
+				{
+					"value": "askInvisible",
+					"label": "ask for permision for invisible <canvas>"
+				},
+				{
+					"value": "blockOnlyBlackList",
+					"label": "block only black list"
+				},
+				{
+					"value": "allowEverything",
+					"label": "allow everything"
+				}
+			]
 		},
 		{
 			"name": "allowPDFCanvas",