diff --git a/src/main/angular/public/error.svg b/src/main/angular/public/error.svg
new file mode 100644
index 0000000..86247dd
--- /dev/null
+++ b/src/main/angular/public/error.svg
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="iso-8859-1"?>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 50 50">
+  <circle style="fill:#D75A4A;" cx="25" cy="25" r="25"/>
+  <polyline style="fill:none;stroke:#FFFFFF;stroke-width:2;stroke-linecap:round;stroke-miterlimit:10;" points="16,34 25,25 34,16"/>
+  <polyline style="fill:none;stroke:#FFFFFF;stroke-width:2;stroke-linecap:round;stroke-miterlimit:10;" points="16,16 25,25 34,34"/>
+</svg>
diff --git a/src/main/angular/src/app/crud/ApiService.ts b/src/main/angular/src/app/crud/ApiService.ts
index 877fb94..3ca66a1 100644
--- a/src/main/angular/src/app/crud/ApiService.ts
+++ b/src/main/angular/src/app/crud/ApiService.ts
@@ -10,13 +10,21 @@ import {RxStompState} from '@stomp/rx-stomp';
 })
 export class ApiService {
 
+  private _connected: boolean = false;
+
+  get connected(): boolean {
+    return this._connected;
+  }
+
   constructor(
     readonly http: HttpClient,
     readonly stomp: RxStompService,
   ) {
+    this.onConnect(() => this._connected = true);
+    this.onDisconnect(() => this._connected = false);
   }
 
-  getNone<T>(path: any[], next?: Next<void>): void {
+  getNone(path: any[], next?: Next<void>): void {
     this.http.get<void>(url('http', path)).subscribe(next);
   }
 
@@ -28,7 +36,7 @@ export class ApiService {
     this.http.get<any[]>(url('http', path)).pipe(map(list => list.map(fromJson))).subscribe(next);
   }
 
-  postNone<T>(path: any[], data: any, next?: Next<void>): void {
+  postNone(path: any[], data: any, next?: Next<void>): void {
     this.http.post<void>(url('http', path), data).subscribe(next);
   }
 
diff --git a/src/main/angular/src/styles.less b/src/main/angular/src/styles.less
index 44f41a7..36e18d7 100644
--- a/src/main/angular/src/styles.less
+++ b/src/main/angular/src/styles.less
@@ -12,9 +12,7 @@ body {
   text-decoration: underline;
 }
 
-.hint {
-  background-color: lightyellow;
-  border: 0.1em solid yellow;
+.message {
   margin: 0.5em;
   padding: 0.25em;
   font-size: 60%;
@@ -25,3 +23,13 @@ body {
     vertical-align: bottom;
   }
 }
+
+.messageInfo {
+  background-color: lightyellow;
+  border: 0.1em solid yellow;
+}
+
+.messageError {
+  background-color: #fdaaaa;
+  border: 0.1em solid red;
+}