If you update to the latest version of the Firefox browser, you may find the WYSIWYG editor in your store will disappear. This is due to a bug in the FCKEditor that is used for this component, it has a browser compatibility check that only goes up to the year 2009! Here's information on how to correct this if you are effected. You'll find the editor in the customtags/fckeditor directory of your store.
FCKEditor Year 2010 Bug