IE8 + jQuery + $.ajax

IE8 + jQuery + $.ajax

Hi there. I have a problem with .ajax function and IE8. Short brief: I use jQuery for ajax requests and have trouble with that in IE8 but in other browsers my code works fine. I can say more. Even IE8 works fine but after manual page refresh (f5, ctrl+r). When page loads first time and I click on ajax item I`ve got error "Object expected" or something like that. 
Now I ask for help. I spent about 3 days on this trouble. Thanks.
My sample code:
  2. <h1>IE Ajax Test</h1>
  3. <a href='javascript:void(0);' id='ajax'>do ajax</a><br/>
  4. <div id='res'></div>
  5. <script type='text/javascript'>
  6. $(document).ready(function(){
  7. if($.browser.msie) alert("IE ver. " + $.browser.version);
  8. $('#ajax').click(function(){
  9. doAjax();
  10. });
  11. });
  12. function doAjax() {
  13. var post_data = "ajax=true";
  14. $.ajax({
  15.             type: 'POST',
  16.             data: post_data,
  17.             url: '<?php echo $this->createUrl('test/ajax');?>',
  18.             success: function(responce) {
  19. $("#res").append(responce + "<br/>");
  20.             }
  21.         });
  22. }
  23. </script>