I am working on this issue too. I have found that you can but it isn't pretty(see returns). The problem I'm working on now is how to save the file back... Editor1.SaveFile() doesn't seem to work for me right now. Maybe it is has to do with allowing edits on serverside code.

Editor1.LoadFile("stylesheet.css")

RETURNS:
body { font-size:100%; font-family:Verdana; color:#000000; background-color:#ffffff; background-image: url(none); background-position:left top; background-repeat:no-repeat; } .rightRegion { font-size:80%; width:25%; } .leftRegion { font-size: 100%; } .headerRegion { font-size:85%; color:inherit; } .bodyRegion { font-size:85%; } .wrap { float:left; padding:0 5px 5px 0; } .page-title { font-size:120%; font-weight:bold; } .menu { color:#000000; font-size:85%; } .menu-title { font-size:120%; font-style:italic; font-weight:bold; border-bottom:solid 1px #cccccc; } .menu-subtitle{ font-size:85%; font-style:italic; font-weight:normal; border-bottom:solid 1px #cccccc; } a { text-decoration:underline; color:#333333; font-size:inherit; } .pageWrapper { width:980px; }