/* Overlay */
#simplemodal-overlay {background-color:#000; cursor:wait;}

/* Container */
#simplemodal-container {height:600px; width:650px; background-color:#fff; border:3px solid #ccc; overflow:scroll}
/*
#simplemodal-container a.modalCloseImg {background:url(/assets/admin/images/icons/remove_24.png) no-repeat; width:25px; height:29px; display:inline; z-index:3200; position:absolute; top:-15px; right:-18px; cursor:pointer;}
*/

#simplemodal-container .modalheader {height:30px; width:90%; background:url(/assets/admin/images/layout/tree_backgr.jpg) repeat-x 0px 0px; color:#0192BF; font-size:1.1em; font-weight:bold; line-height:30px;}
#simplemodal-container .modalheader span {padding-left:8px;}
#simplemodal-container .modalbody {padding:15px 5px 15px 5px;}
#simplemodal-container .modalbody th {text-align:right;}
#simplemodal-container .modalbodysubmitbuttons {text-align:center;}

.modalCloseImg {
	background:url(/assets/site/img/x.png) no-repeat; /* adjust url as required */
	width:25px;
	height:29px;
	display:inline;
	z-index:3200;
	position:absolute;
	top:10px;
	right:42px;
	cursor:pointer;
}
<!--[if lt IE 7]>
<style type='text/css'>
	.modalCloseImg {
		background:none;
		right:-14px;
		width:22px;
		height:26px;
		filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(
			src='img/x.png', sizingMethod='scale'
		);
	}
</style>
<![endif]-->