[poorking]

Куда уж проще.

И так бесконечно.

вот без jQuery

<script type = "text/javascript">
window.onload = function(){
	var img = document.getElementById("myimg"), open = true, width = 300, left = 0;
	
	img.style.position = "absolute";
	img.style.height = "100px";
	
	
	(function(){	
		if(open){
			img.style.left = left ++ + "px";
		}
		
		img.style.width = (open ? width -- : width ++) + "px";
		
		if(width == 0){
			open = false;
		}
		
		if(width == 300){
			open = true;
		}
		
		window.setTimeout(arguments.callee, 10);
	
	}())
	
	
}
</script>

<div class = "wrapper">
	<img id = "myimg" src = "http://javascript.ru/forum/images/ca_serenity/misc/logo.gif"/>
</div>