Make XML+CSS file content editable in firefox -

i have xml document want show in firefox assigned css file. want enable edit/design mode in firedox enable user edit text content. same contenteditable="true" html content. possible xml+css content?

sample.xml

<?xml version="1.0"?> <?xml-stylesheet type="text/css" href="sample.css" ?> <doc>     <red>red text</red>     <blue>blue text</blue>     <green>and... green text</green> </doc> 

sample.css

red {     display: block;     color: red; }  blue {     display: block;     color: blue; }  green {     display: block;     color: green; } 

thanks, ingo