[DynkanMaclaud]

<script type="text/javascript">
    var images = new Array();
    var i = 0;
     
    images[0] = 'images/1.jpg';
    images[1] = 'images/2.jpg';
    images[2] = 'images/3.jpg';
     
  
	
	   function lol() {
        i = i-1;
        if (i < 0) {
            i = images.length-1;
        }
        document.getElementById("img_main").src = images[i];
    };   
	
	 function viewImages() {
        i = i+1;
         if (i == images.length) {
            i = 0;
        }
        document.getElementById("img_main").src = images[i];
        
    };  
	
	
</script>

Вот так то что нужно... СПС Viral