채크박스 check input 클릭시 추가 입력란 나오게

<script language="javascript">
var catan=0
function alla(){
if(catan==1){
etc1.style.display = "none" //숨겼다
catan=0
}else{
etc1.style.display = "block"//내보냈다
catan=1
}
}
</script>
<input type=text name=title class=input size=70 maxlength=255 style='width:100%;'>
<input type='checkbox' onClick="alla()">
<input name='etc1' id='etc1' type='text' style="display:none">