function validate(f) {
if (f.realname.value=="" || f.realname.value==null) { alert("Please, enter your name"); return false }
if (f.address.value=="" || f.address.value==null) { alert("Please, enter your address"); return false }
if (f.Telephone.value=="" || f.Telephone.value==null) { alert("Please, enter your phone number"); return false }
if (f.email.value=="" || f.email.value==null) { alert("Please, enter your e-mail"); return false }
else {
    //we want to check that this is a valid email address format
    var sEmail = f.email.value;
    if (sEmail.indexOf("@")==-1) { alert("e-mail address must contain @"); return false }
    if ((sEmail.length-sEmail.lastIndexOf("."))>4 || (sEmail.length-sEmail.lastIndexOf("."))<=2) { alert("Your e-mail is not valide"); return false}
}
return true;
}