title: Angular 10 iframe first shows 404 page then displays page content
body: <p>Hello i am using bellow HTML code to use iframe and show an external page hosted on the same domain so no wories for cross domain</p>
  <pre><code>&lt;iframe frameborder=&quot;0&quot; [src]=&quot;url&quot;&gt;&lt;/iframe&gt;
  </code></pre>
  <p>and the following typescript code to sanitize and load the content</p>
  <pre><code>this.url = this.sanitizer.bypassSecurityTrustResourceUrl(&quot;/assets/static/page.html&quot;);
  </code></pre>
  <p>the problem is a bit strange after page load, the iframe first shows error 404 for a fraction of second in localhost and for a 2 to 3 seconds in production and then displays the actual page content. This is very irritating as angular has no proper support for iframe events e.g. page load, failure</p>