ALWAYS be sure your opening and closing STYLE tags are present and visible before saving!
If you click Save & Close and the closed </style> tag is not present, the guide will literally go blank and you will not be able to restore it without notifying Springshare and exposing yourself to considerable embarrassment. Also note that there is a CSS limit of 2000 characters. If you exceed that limit any surplus code will be deleted from the end, including the closed </style> tag! Don't click Save & Close until you confirm that both open and closed style tags are visible.