Added simple styling to the error message and the corresponding select element.

src/app/app.component.html

@@ -3,7 +3,7 @@
         <textarea class="textinput" (keyup)="update(step)" placeholder="Please enter your input ..."
                   [(ngModel)]="step.content">{{step.content}}</textarea>
     </div>
-    <div class="selectwrapper">
+    <div [ngClass]="{selectwrapper: true, error: step.error}">
         <div class="arrow_box">
             <select class="select" (change)="convert(step, $event)">
                 <option id="undefined">Select conversion ...</option>