Prova cosi':
codice:
<script>

var it=0
var head="display:''"
function initialize()
{
  mytext=typing.innerText
  var myheight=typing.offsetHeight
  typing.innerText=''
  document.all.typing.style.height=myheight
  typeit()
}

function typeit()
{
  typing.insertAdjacentText("beforeEnd",mytext.charAt(it))
  if (it<mytext.length-1)
  {
     it++
     setTimeout("typeit()",100)
  }
  else
     setTimeout("initialize()",5000) 
}

if (document.all)
  document.body.onload=initialize

</script>
ciao