Test Validasi

<!DOCTYPE html>
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script>
$(function(){
$('#daftar input[name="Daftar"]').click(function(e){
    var valid = 1;
    var ta = $('textarea[name="alamat"]').val();
    if(ta==''){
        $("span.val_alamat").html("Alamat harus diisi.").show();
        valid = 0;
    }

    if(valid==0){
        e.preventDefault();
    }
})
})
</script>
<style>
#error{
    color:red;
    padding:3px;
    display:none;
}
</style>
</head>
<body>
<form id="daftar" action="" method="post">
<textarea name="alamat" cols="50" rows="4"></textarea><span id="error" class="val_alamat"></span>
<p><input type="submit" name="Daftar" value="Simpan" />
</form>
</body>