jquery key up firing multiple time - php

Question

i have this code:
$("#search").keydown(function (e) {
var str = $(this).val();
alert(str);
var url = $("#url").val() + "?ajax=true&q=" + str;
$("#tableWrap").load(url, function () {});
});
#search is id of a textbox that filter information shown in a table. when i type in that for first key the function is firing one time . when i type second key in it the function is firing two time ... .any idea?
Edit:all code.
$(document).ready(function(){
// $("#search").val("جست و جو...");
$("#search").live('click', function(){
$(this).val("");
});
$("#search").keyup(function (e) {
var str = $(this).val();
alert(str);
var url = $("#url").val() + "?ajax=true&q=" + str;
$("#tableWrap").load(url, function(){
});
});
/* $("#search").live('keyup', function(){
var str = $(this).val();
var url = $("#url").val() + "?ajax=true&q=" + str;
$("#tableWrap").load(url, function(){
// $("#search").focus().val(str);
});
});*/
$(".pg_class a").live('click',function(){
showLoading();
$("#load").fadeIn("slow");
loadAJAX(this+"&ajax=true");
return false;
});
$("#tableWrap th").live('click',function(){
showLoading();
$("#load").fadeIn("slow");
loadAJAX($(this).children("a").attr("href") + "&ajax=true");
return false;
});
$("#tableWrap th a").live('click',function(){
showLoading();
$("#load").fadeIn("slow");
//alert($(this).attr("href"));
// alert("salam");
loadAJAX($(this).attr("href") + "&ajax=true");
return false;
});
$(".header select").live('change',function(){
showLoading();
$("#load").fadeIn("slow");
var pageSize = $('.header select option:selected').text();
var url = $('.header select').val();
// alert(url+pageSize+"&ajax=true");
loadAJAX(url+pageSize+"&ajax=true");
});
});
</script>

Answer 1

for future.
i solve the problem with this:
jQuery("#search").one("keyup", function (e) {
var str = $(this).val();
var url = $("#url").val() + "?ajax=true&q=" + str;
$("#tableWrap").load(url, function(){
});
});