<style type="text/css">
.style1 {
        height:30px;
        color:#fff;
}
</style>
<script> $(document).ready(function(){

             $("#btn1").click(function()
                {
                	$('.panel').fadeOut() ;
                    return false;
                });
});
</script>

<div id="btn1"> Button</div>
<div class="panel">Text_Text_Text</div>

$('.panel').addClass('style1') ;

$('.panel').attr('id','style1') ;

$('.panel').attr('id','style1') ;

<div id="btn1"> Button</div>
<div id="btn1"> Button2</div>