Currently, it is possible to align an image using the Justify Tools of RadEditor in IE, Chrome, Safari and Opera, but not in Firefox. In addition the content produced in the different browsers is different.

Provide the ability to select and resize table elements in Chrome and Safari. This feature is already implemented in the docs.google.com web editor by replacing the table cells with div elements and providing resize handlers for them.

Did telerik rich text editor check arabic language with the spell checker ?

When only one word is inside the content of the editor. If you select it and try to apply a desired class name from the mentioned tool, nothing happens. 

In scenarios where RadEditor is moved through the DOM the typical approach is to call the onParentNodeChanged method in order to re-render the editor. In Edge browser this does not work. CleanAtributes filter is alerted as failed and further RadEditor is unresponsive. 

Temporary solution is to switch the content area mode to DIV:

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

Using the delete key in the content area of the RadEditor sometimes cause incorrect behavior to be encountered, e.g., content disappearance, incorrect elements to be removed etc.

For example pressing delete key before a list element, the li tag is removed, instead of just the cursor to be positioned in it.

This behavior comes from the browser and there is no RadEditor logic that interferes with it.

It would be nice if this inconsistencies are handled via custom commands that act more stable across browsers. 

The following issues are fixed with this item:

Pressing backspace in a table sometimes inserts non breaking spaces
Could not complete the operation due to error 800a025e when deleting table columns
Redundand nbsps are added to the content using backspace inside <ul> in IE9
IE10 crashes when nested lists are highlighted and deleted
Incorrect List nesting is generated when a Paragraph is deleted via backspace key under IE11

You can workaround this issue by using this override:

<telerik:RadEditor runat="server" ID="RadEditor1">
    <Content>
        <br/>
        <iframe src="about:blank">Iframe not supported</iframe>
    </Content>
</telerik:RadEditor>

<script>
    Telerik.Web.UI.Editor.Utils._copyElementsBetweenNodes = function (oldNode, newNode, elementName)
    {
        var oldElements = oldNode.getElementsByTagName(elementName);
        var newElements = newNode.getElementsByTagName(elementName);
        for (var i = 0; i < oldElements.length; i++)
        {
            switch (elementName)
            {
                case "script":
                case "title":
                    newElements[i].text = oldElements[i].text;
                    break;
                case "style":
                    if (newElements[i].innerHTML != oldElements[i].innerHTML)
                    {
                        newElements[i].styleSheet.cssText = oldElements[i].styleSheet.cssText;
                    }
                    break;
                case "select":
                    newElements[i].selectedIndex = oldElements[i].selectedIndex;
                    break;
                case "input":
                    if ((oldElements[i].type == 'radio' || oldElements[i].type == 'checkbox') && $telerik.$(oldElements[i]).attr("checked"))
                    {
                        $telerik.$(newElements[i]).attr("checked", "checked");
                        if ($telerik.isIE9Mode && oldElements[i].type == 'checkbox' && oldElements[i].checked)
                        {
                            newElements[i].checked = true;
                            newElements[i].setAttribute("checked", "checked");
                        }
                    }
                    break;
                case "iframe":
                    var innerHTML = oldElements[i].innerHTML;
                    if (innerHTML)
                    {
                        var outerHTML = newElements[i].outerHTML;
                        if (outerHTML)
                        {
                            var gtIndex = outerHTML.indexOf(">");
                            if (gtIndex > 0)
                            {
                                outerHTML = outerHTML.substr(0, gtIndex) + ">" + innerHTML + outerHTML.substr(gtIndex + 1 + innerHTML.length);
                                newElements[i].outerHTML = outerHTML;
                            }
                        }
                    }
                    break;
                default:
                    if (newElements[i].innerHTML != oldElements[i].innerHTML)
                        $E.Utils.setElementInnerHtml(newElements[i], oldElements[i].innerHTML);
                    break;
            }
        }
    };
</script>

Inserting an image after opening ImageManager from within the ImageManager's Properties tab throws JS error. The issue is reproducible both in IE and Firefox

video: http://screencast.com/t/n4T0XYtSpt

Inserting a new line after a link typically adds a new line and removes the copied link. 

However, this does not work when paragraph is about to be split. 

For the time being you can override the _nodeInsertedHandler method to resolve the bug as in this example:

<telerik:RadEditor runat="server" ID="RadEditor1">
     <Content>
         <p><a href="http://www.telerik.com" >link</a>text</p>
     </Content>
 </telerik:RadEditor>

 <script>
     Telerik.Web.UI.Editor.InsertParagraphCommand.prototype._nodeInsertedHandler = function (args) {
         var command = this,
             cursor = args.get_cursor(),
             container = args.get_container(),
             isEmptyContainer = command._isEmptyContainer(container, cursor),
             $E = Telerik.Web.UI.Editor,
             utils = $E.Utils;

         var parentAnchor = utils.getElementParentByTag(cursor, "A");

         if (command._isEmptyContainer(parentAnchor, cursor))
             command._removeNode(parentAnchor);

         if (isEmptyContainer) {
             if (command.get_editor().get_enableTrackChanges()) {
                 var tcUtils = $E.TrackChangesUtils,
                     parentTrackedInsert = tcUtils.getParentTrackChangesInsertNode(cursor, container),
                     parentTrackedDelete = tcUtils.getParentTrackChangesDeleteNode(cursor, container);
                 command._removeNode(parentTrackedInsert);
                 command._removeNode(parentTrackedDelete);
             }
         }
     };
 </script>

It is a common scenario users to start selecting text and accidental trigger mouseup event outside of the content area. Still, the focus is inside RadEditor and InlineEditCompleted event should not fire.

Possible workaround:

<telerik:RadEditor runat="server" ID="RadEditor1" EditType="Inline"
    OnClientLoad="OnClientLoad" OnClientInlineEditCompleted="OnClientInlineEditCompleted">
    <Content>
       some text
    </Content>
</telerik:RadEditor>

<script>
    function OnClientInlineEditCompleted(sender, args) {
        if (sender._editCompleted) {
            alert("Fired!");
        }
    }

    function OnClientLoad(sender, args) {
        $telerik.$(document).on("mouseup", function (e) {
            if (e.target === sender.get_contentArea() || e.target === sender.get_textArea()) {
                sender._editCompleted = true;
            }
        })

        $telerik.$(document).on("mousedown", function (e) {
            if (e.target === sender.get_contentArea() || e.target === sender.get_textArea()) {
                sender._editCompleted = false;
            } else {
                sender._editCompleted = true;
            }
        })
    }
</script>

Having more than one editor on the page, with EditType="Inline", and using dropdown tools causes the event to be raised for the incorrect editor.

For example, using this markup:

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

and this Page_Init code:

protected void Page_Init(object sender, EventArgs e)
{
    RadEditor1.RenderMode = RenderMode.Lightweight;
}

Causes icons to either miss or their position is incorrect.

Instead of null, the String.Empty can be used. 

When user has changed image properties via Image Properties dialog, changes are getting cleared when area is being added via Image Map Editor.