Pass Query String Value to form

Hello all:

I've got a form sitting inside an .aspx page. I would like to populate one of the fields in the form with a querystring value thats passed to the page the form resides on. 

<form method="post" action="">
<input type="text" name="myName" value ="abc" />
<input type="text" name="myDetails" value ="123" />
<input type="text" name="myStuff" value ="" />
</form>

I get the querystring like this:

id = Request.QueryString["dn"];

how do i pass the value of "id" to the input "myStuff" in the code behind?

Any help would be greatly appreciated.