function pass() {
var password = ''
var pas1 = ''
var pas2 = ''
var pas3 = ''
var pos = 0
password=prompt('Introduce la clave:','');
password=password.toLowerCase();
if ((password == '') || (password == null)) {
history.back; 
}
else{
pas1=location.pathname;
pos=pas1.lastIndexOf("/");
pas2=pas1.substring(0,pos+1);
pas3=pas2 + password + ".html";
location.href= pas3;

}
}