Specify Custom CSS for Editor - crpietschmann/jHtmlArea GitHub Wiki

Even though jHtmlArea contains some "default" CSS to use for styling the WYSIWYG editor; it can be overridden to use which ever CSS file necessary to skin the editor to match the web page with which it resides. To do this just set the "css" option parameter when creating the jHtmlArea editor to URL of the desired CSS file.

$('textarea').htmlarea({
    css: '/style//jHtmlArea.Editor.css'
});