Dynamically change form elements with javascript

I'm trying to change the city and state based on the zip code a user enters. This should all be done on the same page with jquery. I found some code elsewhere on this site but couldn't get it to work. Here is the code snippet:

        <script type="text/javascript" src="js/jquery.js"></script>
        <script type="text/javascript" src="js/jquery.validate.js"></script>
        <script type="text/javascript" s开发者_运维技巧rc="js/cufon-yui.js"></script>
        <script type="text/javascript" src="js/Myriad_Pro_700.font.js"></script>
        <script type="text/javascript">

        $("#zip").bind("change", function(e){
          $.getJSON("http://mydomain.com/code.php?zip=" + $("#zip").val(),
                function(data){
                  $.each(data, function(i,item){
                    if (item.field == "city") {
                      $("#city").val(item.value);
                    } else if (item.field == "state") {
                      $("#state").val(item.value);
                    }
                  });
                });
        });

        </script>

and this is my html:

                <label>zip</label>
                <input type="text" name="zip" maxlength="5" id="zip" class="textbox1" />
                <label>first name</label>
                <input type="text" name="fname" class="textbox1" />
                <label>last name</label>
                <input type="text" name="lname" class="textbox1" />
                <label>address</label>
                <input type="text" name="address" class="textbox1" />
                <label>address 2</label>
                <input type="text" name="address2" class="textbox1" />
                <label>city</label>
                <input type="text" name="city" id="city" class="textbox1" />
               <label>state</label>
                <input type="text" name="state" id="state" class="textbox1" maxlength="2" />

The php file outputs the json just fine.

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You are trying to access the inputs by ID and your inputs don't have ID's. Either change your selector or give you inputs ID's.

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The subdomain is inaccurate (as I said in my email). change

...
$.getJSON("http://mydomain.com/code.php?zip=" + $("#zip").val(),
...

to

...
$.getJSON("http://www.mydomain.com/code.php?zip=" + $("#zip").val(),
...