JavaScript

<script language="JavaScript">
function setVisibility(id, visibility) {
document.getElementById(id).style.display = visibility;
}
</script>

HTML

<input type=button name=type value='Show Layer' onclick="setVisibility('sub3', 'inline');";>
<input type=button name=type value='Hide Layer' onclick="setVisibility('sub3', 'none');";> 
<br><br>
<input type=image name=imb src='images/show-layer.jpg'  onclick="setVisibility('sub3', 'inline');";>

<div id="sub3">Message Box<br><a href=hide-layer3.php>Demo using single button</a>
<br><a href=hide-layer4.php>Demo two boxes & single button</a></div>

Style

<style type="text/css">
#sub3 {
position: absolute;
left: 250px;
top: 100px;
background-color: #f1f1f1;
width: 280px;
padding: 10px;
color: black;
border: #0000cc 2px dashed;
display: none;
}