Edit in JSFiddle

 <p>This is the main content. To display a lightbox click <a href = "javascript:void(0)" onclick = "document.getElementById('light').style.display='block';document.getElementById('fade').style.display='block'">here</a></p>
        <div id="light" class="white_content">This is the lightbox content. <a href = "javascript:void(0)" onclick = "document.getElementById('light').style.display='none';document.getElementById('fade').style.display='none'">Close</a></div>
        <div id="fade" class="black_overlay"></div>

.black_overlay{
	display: none;
	position: absolute;
	top: 0%;
	left: 0%;
	width: 100%;
	height: 100%;
	background-color: black;
	z-index:1001;
	-moz-opacity: 0.8;
	opacity:.80;
	filter: alpha(opacity=80);
}

.white_content {
	display: none;
	position: absolute;
	top: 25%;
	left: 25%;
	width: 50%;
	height: 50%;
	padding: 16px;
	border: 16px solid orange;
	background-color: white;
	z-index:1002;
	overflow: auto;
}