jQuery.ajax and page refresh in Firefox

jQuery.ajax and page refresh in Firefox

Couldn't find the answer on the forum.
So my problem is that i can't send form data in FF without page refresh (though in IE7-8 everything works smoothly).
My code fragments:
  1. <input id="f_submit" type="image" src="submit.png"/>
  1. ...
  2. $(document).ready(function(){
  3.       $("#f_submit").click(function(e){
  4.             e.preventDefault();
  5.             $.ajax({
  6.                         async: true,
  7.                         type: "POST",
  8.                         url: "http://../callback.php",
  9.                         data: f_str,
  10.                         dataType: 'html',
  11.                         success: function(result) {...
  12. ...
  13. }