<form id="location_lookup" name="location_lookup" method="get" style="float:left;">
          <div style="float:left;clear:left;margin-bottom:10px;">
              <label for="isbn13">Barcode/Product Code :</label>
              <input id="isbn13" name="isbn13" type="text" value="" />
              <input id="isbn13" name="function" type="hidden" value="lookupProduct" />
          </div>
          <div style="float:left;clear:left;">
              <input type="submit" value="Send" class="bigbutton" />
              <input type="reset" value="Clear" id="formReset" class="bigbutton"/>
          </div>
        </form>

$("#location_lookup").submit(function(event) {
event.preventDefault();

        var isbn13 = $("input[name='isbn13']").val();

        $.ajax({
            url: "location_functions.php",
            type: "get",
            data: values,
            async: false,
            beforeSend: function(x) {
                if(x && x.overrideMimeType) {
                x.overrideMimeType("application/j-son;charset=UTF-8");
                }
            },
            dataType: "json",
            success: function(values){

                //does more stuff...