CSS:

	.show {
		display: block;
	}
	.hide {
		display: none;
	}

 

JavaScript:

window.onload = function() {
	var $ = function(id) {
		return document.getElementById(id);
	};
	
	$("fixAdHead").onmouseover = function() {
		$("fixAdBody").className = "show";
		$("closeBtn").className = "show";
	};
	$("closeBtn").onclick = function() {
		$("fixAdBody").className = "hide";
		$("closeBtn").className = "hide";
	};
};