If the Height of the RadEditor control is set to percentage value, the content area element is too small and does not correspond to the desired stylization. The table element inside the RadEditor wrapper also is calculated with an incorrect height.

A possible resolution is using a custom Client-side function, that sets the correct stylization changes to the table element and the content element. This method should be attached to the editor's OnClientLoad event. Please follow this example setup:

<telerik:RadEditor runat="server" ID="RadEditor1"
	Height="100%" Width="100%" OnClientLoad="OnClientLoad">
</telerik:RadEditor>
<script type="text/javascript">
	function OnClientLoad(editor, args) {
		setTimeout(function () {
			var contentElement = editor.get_contentAreaElement();
			var editorsTable = $get(editor.get_id() + "Wrapper");
			editorsTable.style.height = "100%";
			contentElement.style.height = "100%";
		}, 0);
	}
</script>