diff --git a/lib/network/Network.js b/lib/network/Network.js
index ac0476bb..8e9a39c5 100644
--- a/lib/network/Network.js
+++ b/lib/network/Network.js
@@ -204,6 +204,7 @@ function Network (container, data, options) {
       editError:"The function for edit does not support two arguments (data, callback).",
       editBoundError:"No edit function has been bound to this button.",
       deleteError:"The function for delete does not support two arguments (data, callback).",
+      createEdgeError:"Cannot link edges to a cluster.",
       deleteClusterError:"Clusters cannot be deleted."
     },
     tooltip: {
diff --git a/lib/network/mixins/HierarchicalLayoutMixin.js b/lib/network/mixins/HierarchicalLayoutMixin.js
index b866774d..01f9d25d 100644
--- a/lib/network/mixins/HierarchicalLayoutMixin.js
+++ b/lib/network/mixins/HierarchicalLayoutMixin.js
@@ -57,7 +57,7 @@ exports._setupHierarchicalLayout = function() {
 
     // if the user defined some levels but not all, alert and run without hierarchical layout
     if (undefinedLevel == true && definedLevel == true) {
-      alert("To use the hierarchical layout, nodes require either no predefined levels or levels have to be defined for all nodes.");
+      throw new Error("To use the hierarchical layout, nodes require either no predefined levels or levels have to be defined for all nodes.");
       this.zoomExtent(true,this.constants.clustering.enabled);
       if (!this.constants.clustering.enabled) {
         this.start();
diff --git a/lib/network/mixins/ManipulationMixin.js b/lib/network/mixins/ManipulationMixin.js
index 179a8597..b4bebea8 100644
--- a/lib/network/mixins/ManipulationMixin.js
+++ b/lib/network/mixins/ManipulationMixin.js
@@ -330,7 +330,7 @@ exports._handleConnect = function(pointer) {
     var node = this._getNodeAt(pointer);
     if (node != null) {
       if (node.clusterSize > 1) {
-        alert("Cannot create edges to a cluster.")
+        alert(this.constants.labels["createEdgeError"])
       }
       else {
         this._selectObject(node,false);
@@ -386,7 +386,7 @@ exports._finishConnect = function(pointer) {
     var node = this._getNodeAt(pointer);
     if (node != null) {
       if (node.clusterSize > 1) {
-        alert("Cannot create edges to a cluster.")
+        alert(this.constants.labels["createEdgeError"])
       }
       else {
         this._createEdge(connectFromId,node.id);
@@ -416,7 +416,7 @@ exports._addNode = function() {
         });
       }
       else {
-        alert(this.constants.labels['addError']);
+        throw new Error(this.constants.labels['addError']);
         this._createManipulatorBar();
         this.moving = true;
         this.start();
@@ -450,7 +450,7 @@ exports._createEdge = function(sourceNodeId,targetNodeId) {
         });
       }
       else {
-        alert(this.constants.labels["linkError"]);
+        throw new Error(this.constants.labels["linkError"]);
         this.moving = true;
         this.start();
       }
@@ -481,7 +481,7 @@ exports._editEdge = function(sourceNodeId,targetNodeId) {
         });
       }
       else {
-        alert(this.constants.labels["linkError"]);
+        throw new Error(this.constants.labels["linkError"]);
         this.moving = true;
         this.start();
       }
@@ -524,11 +524,11 @@ exports._editNode = function() {
       });
     }
     else {
-      alert(this.constants.labels["editError"]);
+      throw new Error(this.constants.labels["editError"]);
     }
   }
   else {
-    alert(this.constants.labels["editBoundError"]);
+    throw new Error(this.constants.labels["editBoundError"]);
   }
 };
 
@@ -558,7 +558,7 @@ exports._deleteSelected = function() {
           });
         }
         else {
-          alert(this.constants.labels["deleteError"])
+          throw new Error(this.constants.labels["deleteError"])
         }
       }
       else {
diff --git a/lib/timeline/locales.js b/lib/timeline/locales.js
index 7150dcc7..b78dca3b 100644
--- a/lib/timeline/locales.js
+++ b/lib/timeline/locales.js
@@ -14,7 +14,9 @@ exports['en'] = {
   back: 'Back',
   addDescription: 'Click in an empty space to place a new node.',
   linkDescription: 'Click on a node and drag the edge to another node to connect them.',
-  editEdgeDescription: 'Click on the control points and drag them to a node to connect to it.'
+  editEdgeDescription: 'Click on the control points and drag them to a node to connect to it.',
+  createEdgeError:"Cannot link edges to a cluster.",
+  deleteClusterError:"Clusters cannot be deleted."
 };
 exports['en_EN'] = exports['en'];
 exports['en_US'] = exports['en'];
@@ -35,7 +37,9 @@ exports['nl'] = {
   back: 'Terug',
   addDescription: 'Klik op een leeg gebied om een nieuwe node te maken.',
   linkDescription: 'Klik op een node en sleep de link naar een andere node om ze te verbinden.',
-  editEdgeDescription: 'Klik op de verbindingspunten en sleep ze naar een node om daarmee te verbinden.'
+  editEdgeDescription: 'Klik op de verbindingspunten en sleep ze naar een node om daarmee te verbinden.',
+  createEdgeError:"Cannot link edges to a cluster.",
+  deleteClusterError:"Clusters cannot be deleted."
 };
 exports['nl_NL'] = exports['nl'];
 exports['nl_BE'] = exports['nl'];