function testForm() {
  var fields = ["co_name","cl_tel","cl_name","cl_mes"]
  var ok = true
  for (var i=0; i<fields.length; i++) {
    f=fields[i]
    if (isEmpty(f)) {
      setError(f,errMust)
      ok = false
    }
    else setError(f,"")
  }
  if (!isEmpty("cl_email") && !$("cl_email").value.match(/^[a-z0-9\._]+@[a-z0-9\.\-]+$/i)) {
    setError("cl_email",errMail)
    ok = false
  }
  else setError("cl_email","");
  return ok
}

function $(n){return document.getElementById(n)}

function isEmpty (n) {
  return $(n).value.match(/^\s*$/)
}

function setError (name,text) {
  $(name+"Error").style.display=(text==""?"none":"")
  $(name+"Error").innerHTML=text
}