[jQuery] Get input value from a loaded page

[dearste]

Hi all,
i have load into div a page:

$("#top").load("top.html");

Into top.html thare's a finput like this:

<input type="hidden" id="counter" value="<?=$Count;?>" checked="1" />

How can i do for retrieve some input value??
I have try this

var numsg = $("#counter").val();

but not work.

Thanks.