Here is the simple way to make the visitor not to steal your webpage image or source, You can use this for Any web designs – html/php/asp.net 

Insert this html with your source code

Way 1

<img src=”PicFileName.gif” height=”24″ width=”100″ onContextMenu=”return false;”>
<img src=”PicFileName.gif” height=”24″ width=”100″ onContextMenu=”alert(’Avance Zone Alert!’);return false;”>
<img src=”PicFileName.gif” height=”24″ width=”100″ onContextMenu=”alert(’Visitor! Don\’t Steal my picture!’);return false;”>
Way 2

In body onload call the javascript 
<body onContextMenu =”callme();”>
In head introduce this below lines
<script type=”text/javascript” language=”javascript”>
    function callme()
    {
alert(’Visitor! Don\’t Steal my picture!’);
return false;
}
</script>