idcan only be used once per page. you cannot have 2 elements (or more) having the same identifier.
instead, do this :
<form id="myform">
<div>
<textarea disabled="true"></textarea>
<a class="edit">edit</a>
</div>
<div>
<textarea disabled="true"></textarea>
<a class="edit">edit</a>
</div>
</form>
<script>
$(function(){
$('#myform').on('click','.edit',function(){
$(this)
.siblings('textarea')
.prop("disabled", false)
return false;
});
});
</script>
if you cannot use divs, you can use prev('textarea')instead siblings('textarea')to get the previous text field.