function checkEmailAddress(){ // the HTML5 'email' input will do some of our checking for us. // however this does not solve old/incompliant browsers  document.getElementById('emailResult').innerHTML = "checking..."; email_entered = document.getElementById('emailAddress').value;      length_of_email = email_entered.length; position_of_at  = email_entered.indexOf('@'); another_at      = email_entered.indexOf('@',(position_of_at+1)); position_of_dot = email_entered.indexOf('.');  if(length_of_email<6 || position_of_at==-1 || position_of_dot==-1){  // test 1  document.getElementById('emailResult').innerHTML = "Invalid Email Address Entered"; } else if(another_at>-1){  // test 2 - multiple @ signs  document.getElementById('emailResult').innerHTML = "You have entered multiple '@' signs. Please try again."; } else if(position_of_at==0 || position_of_dot==0){  // the @ and the . cannot be at position 0 for it to be valid.  document.getElementById('emailResult').innerHTML = "An Email address cannot start with an '@' or a '.'"; } else{  document.getElementById('emailResult').innerHTML = "This seems to be a valid email address.";   }}