<img id='img1' src='https:/25D0%25B8-1.jpg'><br><input type='button' onclick='move()'>
<script>
function move() {
document.getElementById('img1').style.margin-right = 20+'%';
}
</script>

document.getElementById("elementID").style.marginRight

<img src="http://javascript.ru/forum/images/smilies/smile.gif" style="position:relative;">

<script>
	var elem = document.getElementsByTagName( 'img' )[ 0 ], i = 0,
		timer = setInterval(
			function() {						
				if ( i === 400 ) clearInterval( timer );
				elem.style.left = i + 'px';
				i += 2;
			},
			30
		);
</script>

<img id='img1' src='http://s1.hostingkartinok.com/uploads/thumbs/2012/03/8d610e5ffba8141a48f3f1978af2e6f8.png'>
<br><input type='button' onclick='a()'>
<script>
function a() {
var i=100;
document.getElementById("img1").style.left = i + 'px';
}
</script>

style="position:relative;"