Making the amazon banner widget width responsive to screen size

Question

I'm trying to insert an Amazon banner in my website, but the width is fixed at only 3 options - 300, 728, and 160. I'm trying to make it responsive as per the screen width by introducing var aax_width = screen.width;

My revised code is as follows:

<script type="text/javascript" language="javascript">
    var aax_height=728;
    var aax_pubname = 'mycode';
    var aax_src='302';
</script>

<script type="text/javascript" language="javascript">
        function aax_punt(){
        var aax_width = screen.width;
        var aax_size= "'" + aax_width + "x" + "90" + "'"
        a='width="'+ aax_width +'" height="'+ aax_height +'"',
        
        html='<iframe src="//c.amazon-adsystem.com/aax2/assoc_lra.html?tag='+aax_pubname+"&c="+aax_channel+"&src="+aax_src+"&sz="+aax_size+'" '+a+' scrolling="no" border="0" marginwidth="0" style="border:none;" frameborder="0"></iframe>',document.write(html),document.close()
    }
    function aax_write(a,e){a.write(e),a.close()}
    function aax_render_ad(a){if(a.passback||"undefined"==typeof a.html||""==a.html)return void aax_punt();var e=a.slotSize;if(!e)return void aax_write(document,a.html);var r=e.indexOf("x"),n=e.substring(0,r),t=e.substring(r+1),c="amznad"+Math.round(1e6*Math.random());
    aax_write(document,'<iframe id="'+c+'" width="'+n+'" height="'+t+'" src="javascript:\'\'" scrolling="no" frameborder="0" marginwidth="0" marginheight="0" bgcolor="#FFFFFF" topmargin="0" leftmargin="0" rightmargin="0" bottommargin="0"></iframe>');
    var i;try{i=document.getElementById(c);var o=i.contentWindow||i.contentDocument;o.document&&(o=o.document),aax_write(o,a.html)}catch(m){i&&(i.style.display="none")}}try{var params={};"undefined"==typeof aax_src&&(aax_src=300),"undefined"==typeof aax_channel&&(aax_channel=100),params.src=aax_src,params.c=aax_channel,params.sz=aax_size,params.ec=0,params.u=document.location,params.ec=0;try{params.u=""+window.top.location}catch(e){}"undefined"==typeof aax_pubname&&(aax_pubname=""),"undefined"!=typeof aax_refurl&&(params.u=aax_refurl),"undefined"!=typeof aax_clickurl&&(params.ct=aax_clickurl),params.cup="undefined"!=typeof aax_clickurlparams?aax_clickurlparams:'{linkCode:"ax1",tag:"'+aax_pubname+'"}',params.pub=aax_pubname;var href="";for(var key in params)href+=key+"="+encodeURIComponent(params[key])+"&";href+="rnd="+Math.round(1e6*Math.random());var aaxserver="aax-eu";("300"==aax_src||"301"==aax_src)&&(aaxserver="aax-us-east"),document.write("<script src='//"+aaxserver+".amazon-adsystem.com/x/getad?jsd=1&"+href+"'/script>"),document.close()}catch(e){aax_punt()}
</script>

But its not working. The error I'm getting is GET http://c.amazon-adsystem.com/aax2/lra/imgs/assoc_lra_s1_in_%271366x90%27.gif?p2 403 (Forbidden).

How do I solve this??