function wrongCaptcha() 
{
  if (document.getElementById('captcha_element')) {
    document.getElementById('captcha_element').style.border="1px solid red";
  }
  alert ("* Codigo de confirmacion incorrecto");
  return false;
}

function isEmail(str) 
{
  var filter = /^([a-zA-Z0-9_.-])+\@(([a-zA-Z0-9_-])+\.)+([a-zA-Z0-9]{2,4})+$/;

  if (filter.test(str)) return true;

  return false;
}

function checkForm(form) {
  var el, elName, value, type;
  var errorList = [];
  var errorText = {
    1 : "* No valida de correo electronico", 
    2 : "* Vaciar el texto del mensaje"
  }
  var errorMsg = "";

  for (var i = 0; i < form.elements.length; i++) {
    el = form.elements[i];
    elName = el.nodeName.toLowerCase();
    value = el.value;
    if (elName == "input") {
      type = el.type.toLowerCase();
      switch (type) {
        case "text" :
          if (el.name == "email") {
            if (!isEmail(value)) {
              errorList.push(1);
              document.getElementById(el.name+'_element').style.border="1px solid red";
            }
            else {
              document.getElementById(el.name+'_element').style.border="0";
            }
          }
          break;
        case "file" :
          break;
        case "checkbox" :
          break;
        case "radio" :
          break;
        default :
          break;
      }
    }
    else if (elName == "textarea") {
      if (value == "") {
        errorList.push(2)
        document.getElementById(el.name+'_element').style.border="1px solid red";
      }
      else {
        document.getElementById(el.name+'_element').style.border="0";
      }
    }
    else if (elName == "select") {
      //if (value == 0) errorList.push(x);
    } 
    else {
      // unknown element type
    }
  }
  if (!errorList.length) {
    return true;
  }
  for (i = 0; i < errorList.length; i++) {
    errorMsg += errorText[errorList[i]] + "\n";
  }
  alert(errorMsg);
  return false;
}