Style the Visual Editor
<?php
//* Do NOT include the opening php tag shown above. Copy the code shown below.
<!--
You can style the visual editor. Simply create your new CSS file – something like editor-style.css and then include the following snippet in your functions
-->
add_filter('mce_css', 'my_editor_style');
function my_editor_style($url) {
if ( !empty($url) )
$url .= ',';
// Change the path here if using sub-directory
$url .= trailingslashit( get_stylesheet_directory_uri() ) . 'editor-style.css';
return $url;
}