ASP.NET

With this simple jQuery function, you can notify a user if they’ve made any un-saved changes to a form field – and give them a chance to save or discard those changes. I was recently able to try this out on a work project and it is working beautifully.
I have a feeling THIS will come in very handy for a variety of projects.

var isDirty = false;
var msg = 'You haven't saved your changes.';

$(document).ready(function(){
   $(':input').change(function(){
      if(!isDirty){
         isDirty = true;
      }
   });

   window.onbeforeunload = function(){
      if(isDirty) {
         return msg;
      }
   };
});