Issue: The value of the href property of a link is changed while modifying the content of the link.

Resolution:

This is a IE's feature and can be prevented by executing "AutoUrlDetect" browser command

<telerik:RadEditor runat="server" ID="RadEditor1" OnClientLoad="OnClientLoad">
</telerik:RadEditor>
  
<script type="text/javascript">
    function OnClientLoad(editor, args) {
        editor.executeBrowserCommand("AutoUrlDetect", false, false);
    }
</script>

More about the matter is available in this thread-- http://stackoverflow.com/questions/3519665/disable-automatic-url-detection-for-elements-with-contenteditable-flag-in-ie