function checkform()
{
//first name 
  if(form1.tfirstname.value == "")
  {
  alert("Please enter your First Name");
  form1.tfirstname.focus();
  return false;
  }
  
//surname 
  if(form1.tsurname.value == "")
  {
  alert("Please enter your Surname");
  form1.tsurname.focus();
  return false;
  }
   
//email address
  if(form1.temail.value == "")
  {
  alert("Please enter an email address");
  form1.temail.focus();
  return false;
  }
  if (form1.temail.value.indexOf("@")  == "-1")
  {
  alert("Please enter a correct email address, it must contain an @ symbol.");
  form1.temail.focus();
  return false;
  }
  
  if (form1.temail.value.indexOf(".")  == "-1")
  {
  alert("Please enter a correct email address, it must contain an . symbol.");
  form1.temail.focus();
  return false;
  }

//address
  if(form1.tcomment.value == "")
  {
  alert("Please enter a comment");
  form1.tcomment.focus();
  return false;
  }
}