If you’re using Adsense on responsive design, this is the code that you can use and it’s NOT against its TOS.

Responsive Adsense Code

<!-- You can add multiple Adsense Ad units -->
<!-- Just change the ad on Line #4 and Line #7 -->
 
<div id="google-ads-1">
 <script type="text/javascript">
 
	adUnit   = document.getElementById("google-ads-1");
	adWidth  = adUnit.offsetWidth;
 
	/* Replace this with your AdSense Publisher ID */
	google_ad_client = "ca-pub-1234567890";
 
	if ( adWidth >= 768 ) {
	  /* Leaderboard 728x90 */
	  google_ad_slot	= "AAA";
	  google_ad_width	= 768;
	  google_ad_height 	= 90;
	} else if ( adWidth >= 468 ) {
	  /* Banner (468 x 60) */
	  google_ad_slot	= "BBB";
	  google_ad_width 	= 468;
	  google_ad_height 	= 60;
	} else if ( adWidth >= 336 ) {
	  /* Large Rectangle (336 x 280) */
	  google_ad_slot 	= "CCC";
	  google_ad_width 	= 336;
	  google_ad_height 	= 280;
	} else if ( adWidth >= 300 ) {
	  /* Medium Rectangle (300 x 250) */
	  google_ad_slot 	= "DDD";
	  google_ad_width 	= 300;
	  google_ad_height 	= 250;
	} else if ( adWidth >= 250 ) {
	  /* Square (250 x 250) */
	  google_ad_slot	= "EEE";
	  google_ad_width 	= 250;
	  google_ad_height 	= 250;
	} else {
	  /* Ad Link Unit (200 x 90) */
	  google_ad_slot 	= "FFF";
	  google_ad_width 	= 200;
	  google_ad_height 	= 90;
	} 
 </script>
 
 <script type="text/javascript"    
   src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
 </script>
</div>