// a function to validate an email address
function send_if_valid()
{ 
  // look for an @ character
  if( document.forms.f.email.value.indexOf("@")== -1 )
  {
    fail("No '@' in address");                       
  }
  else
  {                                                  
    var adr = document.forms.f.email.value.split("@");
    // look for part address before the @ character
    if(adr[0].length < 1 ) fail("User address absent");
    else // look for a dot
    if(adr[1].indexOf(".")== -1) fail("No dot");   
    else // look for domain name after the @ character
    if(adr[1].length < 3) fail("Domain incorrect");
    // if ok send the form data
    else document.forms.f.submit(); 
  }                              
}                                               

// a function to display an error message
function fail(msg)
{                          
  alert("Email Address Error:\n" +msg); 
}