core.js:7873 Can't bind to 'ngIf' since it isn't a known property of 'div'. code example

Example 1: Can't bind to 'ngForOf' since it isn't a known property of 'div'.

// older Angular versions
// import {BrowserModule, CommonModule} from '@angular/common';

import { BrowserModule } from '@angular/platform-browser'
..
..
@NgModule({
  imports: [BrowserModule, /* or CommonModule */],
  ..
})

Example 2: core.js:12799 Can't bind to 'ngForIn' since it isn't a known property of 'ng-container'.

<!--I typed in instead of 'of' in the ngFor expression.-->
<div *ngFor="#talk of talks">