jquery ajax function not working

my html goes like this ,

<form name="postcontent" id="postcontent">
    <input name="postsubmit" type="submit" id="postsubmit" value="POST"/>
    <textarea id="postdata" name="postdata" placeholder="What's Up ?"></textarea>
</form>

The jquery code is as follows

$("#postcontent").submit(function(e) {
    $.ajax({
        type:"POST",
        url:"add_new_post.php",
        data:$("#postcontent").serialize(),
        beforeSend:function(){
            $(".post_submitting").show().html("<center><img src='images/loading.gif'/></center>");
        },success:function(response){   
            //alert(response);
            $("#return_update_msg").html(response); 
            $(".post_submitting").fadeOut(1000);                
        }
    });
});

When I click on the submit button , my ajax request is not working , it looks as if the control is being passed to the JQuery submit function , but the ajax request is not executing/working properly,what is wrong ?