By default, Internet Explorer converts all relative links to
absolute on the client. This behavior is due to the DOM engine of the
Internet Explorer browser which “fills” the paths (href or src) for the
objects in an editing area. The problem does not apply to Firefox. To fix this, RadEditor provides a link stripping
mechanism based on regular expressions that strips absolute paths in
Internet Explorer and fixes the problem. You can read the following KB article for more information on the topic: Stripping image and anchor paths in RadEditor v5.x - v7.x.
Hope this is helpful.
the Telerik team