var banner=new Array()

banner[0]='<img src="img/t1.gif" alt="Pagina Principal" width="496"height="20" border="0"></a>'

banner[1]='<img src="img/t2.gif" alt="Pagina Principal" width="496"height="20" border="0"></a>'

banner[2]='<img src="img/t3.gif" alt="Pagina Principal" width="496" height="20" border="0"></a>'

banner[3]='<img src="img/t4.gif" alt="Pagina Principal" width="496" height="20" border="0"></a>'

banner[4]='<img src="img/t5.gif" alt="Pagina Principal" width="496" height="20" border="0"></a>'

var whichbanner=Math.floor(Math.random()*(banner.length))
document.write(banner[whichbanner])