function validemail(addr) {   // sub function to validate correctness of e-mail address entry.

    var poa = addr.indexOf("@",1);
    var ivc = " /:,;"
    
    if (addr == "") {alert("Please enter your e-mail address."); return false}
    
    for(i=0; i<ivc.length; i++) { 
       badch = ivc.charAt(i);
       if (addr.indexOf(badch) > -1) {
        alert("Invalid character in e-mail address.\n\(cannot be a space or / or : or , or ;\) ");
        return false;
       } 
    }
    
    if (poa == -1 || addr.indexOf("@", poa+1) != -1) {
        alert("Email address must contain an @ but only one @.");
        return false;
       } 
      
    if (addr.indexOf(".", poa+1) == -1) {
        alert("Email address must contain at least one  .  after the @.");
        return false;
       } 
    
  return true
 }