Currently RadNotification uses a single 3D set of icons for all skins. Metro styling, however, requires flat icons.

With the current implementation such  visualization can be achieved by putting a custom icon using the ContentIcon and TiteleIcon properties. 

Under IE an embed tag is generated for the sound. It seems it has default height, so when it is appended to the form with JavaScript it may cause scrollbars if it has siblings with height set to 100%.
There are three possible workarounds
- set the form overflow to hidden with CSS, e.g. html, body, form { height: 100%; overflow: hidden; }
- remove the ShowSound property if it is less important than scrollbars and page layout
- use the following JavaScript function to remove the height from the embed tag:
		function pageLoad()  //Sys.Application.Load handler
		{
			if ($telerik.isIE)
			{
				var embed = $get("<%=rn.ClientID %>" + "_playAudio");
				if (embed && embed.tagName.toLowerCase() == "embed")
					embed.style.display = "none";
			}
		}
where rn is the server ID of the notification control. If more than one RadNotification is present on the page the procedure would have to be repeated for each one.

A workaround is to set the icon URL from the server in order to resolve the URL yourself. For example:

<telerik:RadNotification ID="rnNotInstalledLicense" runat="server" AutoCloseDelay="0" 
						 ShowCloseButton="true" Height="130px" Width="350px" VisibleTitlebar="true"
						 ContentIcon="~/images/install_dataagent.gif"
						 EnableEmbeddedSkins="false" />
<asp:Button ID="Button1" Text="show notification" OnClientClick="showNotification();

return false;" runat="server" />
<script>
	function showNotification() {
		$find("<%=rnNotInstalledLicense.ClientID%>").show();
	}
</script>

and on the server:

C#:
protected void Page_Load(object sender, EventArgs e)
{
	if(!IsPostBack)
	{
		rnNotInstalledLicense.ContentIcon = Page.ResolveUrl(rnNotInstalledLicense.ContentIcon);
	}
}


VB:
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
	If Not Page.IsPostBack Then
		rnNotInstalledLicense.ContentIcon = Page.ResolveUrl(rnNotInstalledLicense.ContentIcon)
	End If
End Sub

When you open a RadNotification in a scrolled page in Edge, it will appear higher than expected or it might not appear at all depending on how much the page is scrolled. 

You can avoid the issue by placing the following script at the end of your page:

		<script type="text/javascript">
			Telerik.Web.UI.RadNotification.prototype._originalSetPopupValue = Telerik.Web.UI.RadNotification.prototype._setPopupVisible;
			Telerik.Web.UI.RadNotification.prototype._setPopupVisible = function(x, y) 
			{
				if (Telerik.Web.Browser.edge) {
					var offsetY = window.pageYOffset;
					var offsetX = window.pageXOffset;

					if (document.documentElement.scrollTop == 0 && document.body.scrollTop > 0)
						y += offsetY;
					if (document.documentElement.scrollLeft == 0 && document.body.scrollLeft > 0)
						x += offsetX;
				}
				this._originalSetPopupValue(x, y);
			}
		</script>

RadNotification plays no sound on mobile devices running iOS, Android and Windows RT.

For the time being you can use the following workaround:
CSS:
	<style>
	 .RadNotification .rnContentWrapper .rnIcon:before {
			font-size: 0.7em\9;
		}
		_:-ms-fullscreen, :root .RadNotification .rnContentWrapper .rnIcon:before {
			font-size: 0.7em;
		}
	</style>
ASPX:
		<telerik:RadNotification ID="RadNotification1" runat="server" AutoCloseDelay="99999" ShowInterval="1000" Position="Center" RenderMode="Lightweight" Text="Project deleted successfully!" VisibleTitlebar="false">
		</telerik:RadNotification>

The issue is reproducible when scroll is applied on the page and when the button showing the notification is in UpdatePanel

JavaScript error is thrown then multiple RadNotification instances with enabled audio are shown.

Error message:

[Intervention] Blocked attempt to create a WebMediaPlayer as there are too many WebMediaPlayers already in existence. See crbug.com/1144736#c27