function lib_bwcheck(){
this.ver=navigator.appVersion
this.agent=navigator.userAgent
this.dom=document.getElementById?1:0
this.opera5=(navigator.userAgent.indexOf("Opera")>-1 && document.getElementById)?1:0
this.ie5=(this.ver.indexOf("MSIE 5")>-1 && this.dom && !this.opera5)?1:0; 
this.ie6=(this.ver.indexOf("MSIE 6")>-1 && this.dom && !this.opera5)?1:0;
this.ie4=(document.all && !this.dom && !this.opera5)?1:0;
this.ie=this.ie4||this.ie5||this.ie6
this.mac=this.agent.indexOf("Mac")>-1
this.ns6=(this.dom && parseInt(this.ver) >= 5) ?1:0; 
this.ns4=(document.layers && !this.dom)?1:0;
this.bw=(this.ie6 || this.ie5 || this.ie4 || this.ns4 || this.ns6 || this.opera5)
return this
}
var bw=new lib_bwcheck()
var a = Math.floor((Math.random()*3));
var banner;
if (a==0) banner='<a href="http://www.jb.com.br/assina.html"><img src="http://www.jb.com.br/mundomedia/banner1.gif" alt="Assine o JB" border="0" width="468" height="60"></a>'
if (a==1) banner='<a href="http://www.jb.com.br/assina.html"><img src="http://www.jb.com.br/mundomedia/banner2.gif" alt="Assine o JB" border="0" width="468" height="60"></a>'
if (a==2) banner='<a href="http://www.jb.com.br/assina.html"><img src="http://www.jb.com.br/mundomedia/banner3.gif" alt="Assine o JB" border="0" width="468" height="60"></a>'
if (bw.ie||bw.ne6)
{
   document.write('<iframe src="http://www.jb.com.br/mundomedia/b_cadernob.htm" target="_blank" scrolling="no"  hspace="0" vspace="0" frameborder="0" marginheight="0" marginwidth="0" width="468" height="60">');
   document.write('</iframe>')
}
else{document.write(banner);}