If you create a link with a target="_blank" attribute, the corresponding value shows as selected. When  the Link Manager is opened second time the value shows as selected, but the link is not set without a target attribute.

You can find attached a sample project, in which is used the Custom Built-In dialogs approach to resolve the problem. For details about this approach follow this link: 
http://demos.telerik.com/aspnet-ajax/editor/examples/externaldialogspath/defaultcs.aspx

The tools are not respected by the toolgroups under IE7 and IE7 standards. This issue causes incorrect layout at resizing and overlay issues of floated tools.
The problem is introduced because the toolgroup elements does not have a properly set width. 

Possible resolution is setting a proper width to every UL at the load event of the editor:

<telerik:RadEditor runat="server" ID="RadEditor1" 
	OnClientLoad="OnClientLoad"></telerik:RadEditor>


<script type="text/javascript">
	function OnClientLoad(editor, args) {
		if (editor.isVisible()) {
			fixToolbarsInIE(editor);
		} else {
			editor.add_firstShow(function () {
				setTimeout(function () {
					fixToolbarsInIE(editor);
				}, 0);
			})
		}
	}

	function fixToolbarsInIE(editor) {
		if ($telerik.isIE) {
			var $ = $telerik.$;
			var editorID = editor.get_id();
			var topTD = document.getElementById(editorID + "Top");
			var toolGroupElements = $(topTD).find(".reToolbar");

			for (var i = 0, l = toolGroupElements.length; i < l; i++) {

				calculateTools(toolGroupElements[i]);
			}
		}
	}

	function calculateTools(toolGroup) {
		var tools = toolGroup.children;
		var size = 0;

		for (var i = 0, l = tools.length; i < l; i++) {
			var tool = tools[i];
			size += tool.offsetWidth;
		}
		toolGroup.style.width = size + "px";
	}
</script>

The mentioned delete operations are not working as expected and consistent across the major browsers. This behavior is casing the Track Changes feature to be unavailable and unusable in some cases.

RadEditor's content is messing up when links are generated through document manager and submit it from Preview mode. The issue is reproducible in Internet Explorer 7

However, a possible workaround for the issue would be to set the following code the OnClientSubmit event of the RadEditor:

<telerik:RadEditor OnClientSubmit = "OnClientSubmit" />
 
<script>
   function OnClientSubmit(editor)
   {
   editor.set_mode(1); //Force design mode
   }
</script>

Inline commands such as bold, italic, underline doesn't trigger each time with empty selection in Internet Explorer.

The paste functionality in RadEditor does not work when EnableTrackChanges property is set to true.  This behavior is observed under Chrome and Safari.

When text is pasted in RadEditor with ContentAreaMode="Div" under Firefox and Chrome, the cursor will be positioned before the pasted text.

In the ImageManager when using AsyncUpload as the upload manager control, the uploaded image is not selected. This prevents a fluent workflow of upload and insert of the image.

The image preview should react in a contextual way when deleting the image as well. Then the previewer should stay empty as is the case with a first load of the dialog.

The StripFormattingOptions feature does not work when the ContentAreaMode is set to Div mode. This behavior is introduced only in Chrome, Firefox and Internet Explorer 7.

 If there are textarea tags or style tags in the HTML content of RadEditor, after completing the spell check  the content is repeated several times. 

The Bold, Italic, Underline, Subscript and Superscript commands do not work in a combination with EnableTrackChanges="true" and ToolbarMode="RibbonBar".

Content appears double if there is a Style element inside it and the Spell Check is triggered.

If a TabStrip with two editors is configured, the editor in the first tab is working correctly, but if the second is shown - its toolbar is not working as expected.

Possible resolution is to insert a meta tag in the head element of the main page, which sets the rendering engine of IE10:
<meta http-equiv="x-ua-compatible" content="IE=10" />

Another possible resolution is to call the onParentNodeChanged() method after the tab is selected:

<telerik:RadTabStrip ID="RadTabStrip1" runat="server" SelectedIndex="0"
    MultiPageID="RadMultiPage1"
    OnClientTabSelected="OnClientTabSelected">
    <Tabs>
        <telerik:RadTab runat="server" PageViewID="RadPageView1" Selected="True" Text="Root RadTab1">
        </telerik:RadTab>
        <telerik:RadTab runat="server" PageViewID="RadPageView2" Text="Root RadTab2">
        </telerik:RadTab>
    </Tabs>
</telerik:RadTabStrip>
<telerik:RadMultiPage ID="RadMultiPage1" runat="server">
    <telerik:RadPageView ID="RadPageView1" runat="server" Width="100%" Selected="True">
        <telerik:RadEditor ID="RadEditor1" runat="server">
            <Content>
                Content Page 1
            </Content>
            <TrackChangesSettings CanAcceptTrackChanges="False" />
        </telerik:RadEditor>
    </telerik:RadPageView>
    <telerik:RadPageView ID="RadPageView2" runat="server" Width="100%">
        <telerik:RadEditor ID="RadEditor2" runat="server">
            <Content>
                Content Page 2
            </Content>
            <TrackChangesSettings CanAcceptTrackChanges="False" />
        </telerik:RadEditor>
    </telerik:RadPageView>
</telerik:RadMultiPage>

<script type="text/javascript">
    function OnClientTabSelected(sender, args) {
        var tabIndex = args.get_tab().get_index();
        if (tabIndex === 1) {
            var editor = $find("<%= RadEditor2.ClientID %>");
            editor.onParentNodeChanged();
        }
    }
</script>

The "Link to original" property should insert an image link pointing to the original image and the "Open in a new window" property should add the target attribute to the link with value "_blank". 
None of these modifications happen if the properties are set to true.

Possible workaround is to add the attached ImageManager dialog as an external dialog using the ExternalDialogsPath property of the RadEditor control. If you need step-by-step example for such approach you could follow this live example: http://demos.telerik.com/aspnet-ajax/editor/examples/externaldialogspath/defaultcs.aspx

Since document.selection is no longer supported in IE11 all occurrences in the code of RadEditor need to be updated accordingly.

When creating a tree view with nodes which on click create instances of the RadEditor and pasting inside the content of the second instance throws a JavaScript error.

The following workaround will help you avoid this behavior:

Set this function to the OnClientLoad property (OnClientLoad = 'OnLoad')

function OnLoad(editor, args) {
var originalGetPasteIFrame = Telerik.Web.UI.Editor.Utils._getPasteIframe;
Telerik.Web.UI.Editor.Utils._getPasteIframe = function (parentDoc, editor) {
if ($telerik.isIE8) {
$telerik.$(this._pasteIframe).remove();
this._pasteIframe = null;
}
return originalGetPasteIFrame.call(this, parentDoc, editor);
}
}

When pasting content between two RadEditors a span with an additional style attribute is generated in Chrome.

The toolbar doesn't show when its mode is ShowOnFocus and PageTop in IE11

A possible resolution is to attach a function to the editor's "focusin" event, the logic of which is to force the visibility state of the toolbar. You can examine the following example:

<telerik:RadEditor runat="server" ID="RadEditor1" 
	ToolbarMode="ShowOnFocus" OnClientLoad="OnClientLoad">

</telerik:RadEditor>

<script type="text/javascript">
	function OnClientLoad(editor, args) {
		editor.attachEventHandler("focusin", function (e) {
			var toolAdapter = editor.get_toolAdapter();

			setTimeout(function () {
				var isVisible = toolAdapter._toolbarHolder ? toolAdapter._toolbarHolder.isVisible() : false;
				if (!isVisible) {
					toolAdapter._showToolbarHolder(true);
				}
			}, 0)
		});
	}
</script>