Using the RadEditor with Auto or Mobile mode in a RadWindow is impossible because JS error are thrown when dialog is shown. 

For the time being, the most proper solution for this case is using the Lightweight mode for RadEditor.

The dragging clue element is shown before the actual dragging of the element in the Grid is initiated (immediately after the item is clicked). The problem is reproducible in Chrome.

Comment: The problem is not reproducible in the following TreeView demo:
http://demos.telerik.com/aspnet-ajax/treeview/examples/functionality/draganddropnodes/defaultcs.aspx

Steps to reproduce:
1. Open http://demos.telerik.com/aspnet-ajax/grid/examples/columns-rows/rows/drag-and-drop/defaultcs.aspx
2. Click over an item (just mouse-down, without moving the mouse nor full click)
Result: The dragging clue is shown without actual moving of the mouse pointer

The issue is caused by a bug in the KB3057839 windows update. The bug has been reported to Microsoft and can be tracked at the following link:

https://connect.microsoft.com/VisualStudio/feedback/details/1475291

Currently the only workaround is to revert the KB3057839 update on the production server.

The grid adds the correct Aria-Selected attribute, but JAWS does not work

A sample project for reproducing the issue is attached:

Each of the pages in the ContentUrl properties has an alert("PageName") displayed at pageLoad.

1, Brows the Default.aspx - an alert - page1 occurs

2. Select Level 2 tab, which would load the subTab - Page4 and the "page4" alert should be shown.

Problem : In addition to the "page4" alert - the "page5" alert is raised and the page5.aspx had been loaded along with page4.aspx.

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Workaround:
To workaround this issue, set the PageViewID property of the parent tab to be with the same value as the PageViewID property on the selected child tab.

<telerik:RadTabStrip runat="server" ID="RadTabStrip1" MultiPageID="rmpPages" Width="100%">
    <Tabs>
        <telerik:RadTab Text="Level 1" Selected="true" PageViewID="page1">
            <Tabs>
                <telerik:RadTab Text="Page 1" PageViewID="page1" Selected="true" />
                <telerik:RadTab Text="Page 2" PageViewID="page2" />
                <telerik:RadTab Text="Page 3" PageViewID="page3" />
            </Tabs>
        </telerik:RadTab>
        <telerik:RadTab Text="Level 2" PageViewID="page4">
            <Tabs>
                <telerik:RadTab Text="Page 4" PageViewID="page4" Selected="true" />
                <telerik:RadTab Text="Page 5" PageViewID="page5" />
                <telerik:RadTab Text="Page 6" PageViewID="page6" />
            </Tabs>
        </telerik:RadTab>
    </Tabs>
</telerik:RadTabStrip>

<telerik:RadMultiPage runat="server" ID="rmpPages">

    <telerik:RadPageView runat="server" ID="page1" ContentUrl="page1.aspx" Selected="true" />
    <telerik:RadPageView runat="server" ID="page2" ContentUrl="page2.aspx" />
    <telerik:RadPageView runat="server" ID="page3" ContentUrl="page3.aspx" />
    <telerik:RadPageView runat="server" ID="page4" ContentUrl="page4.aspx" />
    <telerik:RadPageView runat="server" ID="page5" ContentUrl="page5.aspx" />
    <telerik:RadPageView runat="server" ID="page6" ContentUrl="page6.aspx" />

</telerik:RadMultiPage>

The long code lines in the QSF code viewer are very hard to read as the only way to get the horizontal scroll-bar is to reach the bottom of the page.

Under IE10 and 11 the CrossFade animation causes a random flickering. 

Adding CSS styles for the table layout via the TableCssLayoutTemplates adds the style element inside the body, which is non W3C compliant content.