var rutaimagen = new Array(
					"banner_01.jpg","banner_02.jpg","banner_03.jpg","banner_04.jpg","banner_05.jpg","banner_06.jpg","banner_07.jpg","banner_08.jpg"
					)					
                    var ran_number=Math.round(Math.random()*7); 
					imgselect = rutaimagen[ran_number];
					//alert(imgelect);
					document.getElementById('ad').innerHTML='<IMG SRC="images/'+imgselect+'"  BORDER="0" ALT="">';