function checking(){
  if(!document.all.name.value &&
     !document.all.email.value &&
     !document.all.feedback.value){
    alert('Please enter your name, e-mail address, and any comments you may have.');
    document.all.name.focus();
return false
  }
  if(!document.all.email.value &&
     !document.all.feedback.value){
    alert('Please enter your e-mail address and your comment.');
    document.all.email.focus();
return false
  }
  if(!document.all.name.value &&
     !document.all.feedback.value){
    alert('Please enter your name and your comment.');
    document.all.name.focus();
return false
  }
  if(!document.all.name.value &&
     !document.all.email.value){
    alert('Please enter your name and e-mail address.');
    document.all.name.focus();
return false
  }
  if(!document.all.name.value){
    alert('Please enter your name.');
    document.all.name.focus();
return false
  }
  if(!document.all.email.value){
    alert('Please enter your e-mail address.');
    document.all.email.focus();
return false
  }
  if(!document.all.feedback.value){
    alert('Please enter your comments.');
    document.all.feedback.focus();
return false
  }
}
function thankyou(){
  var custname = document.all.name.value;

  alert('Thank You ' + custname + '.');
}
function immediatefocus(){
  document.all.name.focus();
}
function isavalidemail(inputvalue){

  var foundAt = false
  var foundDot = false
  var atPosition = -1
  var dotPosition = -1

for (var i=0; i<=inputvalue.length; i++) {
  if (inputvalue.charAt(i) == "@") {
      foundAt = true
      atPosition = i
  }
  else if (inputvalue.charAt(i) == ".") {
     foundDot = true
     dotPosition = i
  }
}
if ((foundAt && foundDot) && (atPosition < dotPosition)) {
  return true
}
else {
  alert("Sorry, the e-mail address you entered is not valid, it must contain at least an @ symbol and a period.");
  return false
  }
}