title: Check if web form values have changed
body: <p>I have a multi-step form and user can navigate to any page to modify or add information. There is a menu that shows the current progress, the steps the user has completed, and allows to navigate to any completed or pending step.</p>
  
  <p>In spite of a big button "Save and Continue" some users click this menu to navigate further. I have to check - if values have changed in a form and ask: "Save changes? Yes/No". </p>
  
  <p>What is the best way (with minimum client-side JavaScript code) you suggest me to check if form values have changed?</p>
  
  <p><strong>Edited a bit later:</strong></p>
  
  <p>I forgot to tell that the multi-step form uses postback between steps.</p>