function validate(f) {
    if (f.name.value == "") {
      alert("Please enter your name");
      f.name.focus();
      return false;
    }

    if (f.phone.value == "") {
      alert("Please enter your phone number");
      f.phone.focus();
      return false;
    }

    if (f.email.value == "") {
      alert("Please enter your email address");
      f.email.focus();
      return false;
    }

    if (isEmail(f.email.value) == false) {
      alert("Please enter a valid email address");
      f.email.select();
      return false;
    }

    if (f.message.value == "") {
      alert("Please enter your message");
      f.message.focus();
      return false;
    }
    return true;
  }

  function isEmail(string) {
    if (string.search(/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/) != -1)
      return true;
    else
      return false;
  }