function validateFormOnSubmit(theForm) {
var reason = "";

  reason += validatename(theForm.name);
  reason += validatename(theForm.email);
  reason += validatename(theForm.details);

if (reason != "") {
    alert("Some fields need correction:\n" + reason);
    return false;
  }

  return true;
}

function validatename(fld) {
    var error = "";
 
    if (fld.value.length == 0) {
        fld.style.background = 'yellow'; 
        error = "Fields marked in yellow are required.\n"
    } 

    return error;  
}