I’ve had a few questions/comments on using Custom Styles with FCK Editor, so here’s a style that I created that will format any link you apply it to as a red button that changes color on mouse over.

Add this CSS to the fck.css and portal.css files in you PORTALS folder.

/* Both variations --a.color-- and --span.color a--
    are needed to handle DNN's span applications
    not being consistent */

.red_button, a.red_button:link, a.red_button:visited,
 span.red_button a, span.red_button a:link,
 span.red_button a:visited {
        font-weight: bold;
	color: #FFF;
	padding:4px 8px;
	text-decoration: none;
	border-top: 1px solid #DFDFDF;
	border-left: 1px solid #DFDFDF;
	border-bottom: 1px solid #333;
	border-right: 1px solid #333;

a:hover span.red_button,
span.red_button a:hover {
	border-top: 1px #31557f solid;
	border-left: 1px #31557f solid;
	border-bottom: 1px #666666 solid;
	border-right: 1px #666666 solid;

Be sure to add the following to the fck.xml file, to append the style to the menu in the FCK editor.

<Style name="red_button" element="span">
  <Attribute name="class" value="red_button" />

Hope this helps, post any questions in the comments.