Ajax and Forms: Fix link to prefilters documentation

Fixes jquerygh-502

Author: scottgonzalez

page/ajax/ajax-and-forms.md

@@ -6,7 +6,7 @@ attribution:
   - jQuery Fundamentals
 ---
 
-jQuery's ajax capabilities can be especially useful when dealing with forms. There are several advantages, which can range from serialization, to simple client-side validation (e.g. "Sorry, that username is taken"), to [prefilters](http://api.jquery.com/extending-ajax/#Prefilters) (explained below), and even more!
+jQuery's ajax capabilities can be especially useful when dealing with forms. There are several advantages, which can range from serialization, to simple client-side validation (e.g. "Sorry, that username is taken"), to [prefilters](http://api.jquery.com/jQuery.ajaxPrefilter/) (explained below), and even more!
 
 ### Serialization