The <br> tag is added in the empty content area by Firefox. This tag is stripped by the ConvertToXhtml filter and if you set the ContentFilters property to None, the <br> tag will remain.
Nevertheless, you can find an example demonstrating how to convert the float inline style to align attribute in the following forum thread: http://www.telerik.com/community/forums/aspnet-ajax/editor/editor-transforming-align-right-into-float-right.aspx
the Telerik team
Register for the Q2 2011 What's New Webinar Week. Mark your calendar for the week starting July 18th and book your seat for a walk through of all the exciting stuff we will ship with the new release!