[Deff]

nraw,

<script type="text/javascript">
function ONNnclick(){
  if (document.getElementById("tb1").checked) {// alert("A")
document.getElementById("tbnum").disabled=false;
  }
  else {
document.getElementById("tbnum").disabled=true;
  }
}
</script>


<input  id="tb1" type="checkbox"  checked="false" onclick="ONNnclick()" autocomplete="off"/>
<input  id="tbnum" type="text" value="Тра-та-та"/>
<script type="text/javascript">
document.getElementById("tb1").click()
</script>