Display html containing iFrame in Windows Form c#

i am creating a window application as well as a web application using c#. Scenario is like below:
1. Admin will post messages using Wysiwyg editor( i am using tinyMCE) from the website
2. User will have windows form that will be download the message and display it on the form.
I have taken a webBrowser control to display it. its working fine to display html( formatted text along with picture). problem occurs when we want to display video on it.

I am using following code for that: webBrowser1.Navigate("about:blank");

            HtmlDocument doc = this.webBrowser1.Document;
            doc.Write(String.Empty);
            string strHTML="&lt;p&gt;&lt;iframe src=&quot;http://www.youtube.com/embed/xXdDjnVM1kI&quot; frameborder=&quot;0&quot; width=&quot;425&quot; height=&quot;350&quot;&gt;&lt;/iframe&gt;&lt;/p&gt;\r\n&lt;p&gt;&lt;span style=&quot;color: #ff0000; font-size: xx-large;&quot;&gt;Hi, &lt;/span&gt;&lt;/p&gt;\r\n&lt;p&gt;&lt;span style=&quot;color: #33cccc; font-size: large;&quot;&gt;Enjoy Ganganam Style&lt;/span&gt;&lt;/p&gt;\r\n&lt;p&gt;&amp;nbsp;&lt;/p&gt;";
            string strDecoded=System.Net.WebUtility.HtmlDecode(strHTML);             
            webBrowser1.DocumentText = strDecoded;

Its showing me security alert while running it:

When i add these sites in the trusted site, it works fine. but i want to get ride of these security warning. for that i have tried webBrowser1.ScriptErrorsSuppressed = true;, but its not working also. and also tried How to programmatically answer "Yes" to WebBrowser control security alert.
When webBrowser1.ScriptErrorsSuppressed = true; then iFrame come like below: But i have Adobe Flash Player, and i can play the video by adding the warning site in the trusted sites manually.