function valid_email(email) {
    invalidChars = " /:,;"
    if (email == "") 
    {						// cannot be empty
	    return false
    }

    for (i=0; i<invalidChars.length; i++) {	// does it contain any invalid characters?
		badChar = invalidChars.charAt(i)
		if (email.indexOf(badChar,0) > -1) {
			return false
		}
	}
	atPos = email.indexOf("@",1)			// there must be one "@" symbol
	if (atPos == -1) {
		return false
	}
	if (email.indexOf("@",atPos+1) != -1) {	// and only one "@" symbol
		return false
	}
	periodPos = email.indexOf(".",atPos)
	if (periodPos == -1) {					// and at least one "." after the "@"
		return false
	}
	if (periodPos+3 > email.length)	{		// must be at least 2 characters after the "."
		return false
	}
	return true
}


function valid_form()
{
    var msg = "";
    if (document.getElementById("first_name").value == "")
        msg = msg + "\nPlease enter your name.";
    if (!(valid_email(document.getElementById("email").value) ||
        document.getElementById("phone").value != ""))
        msg = msg + "\nPlease enter your phone number or email address.";
    if (msg != "")
        alert(msg)
  
    return (msg == "");
}