When editing content in the TinyMCE editor, it would be nice for the text to look like it will once you publish the content. In previous versions of WordPress, there was no easy way to do this. You had to do some hacks to get the visual editor to display your style sheet.
Style the TinyMCE Visual Editor
To style the editor so your content in the dashboard looks like the content your publishing, you simply add the following to you functions.php file of your theme: