Webform confirmation message on same reloaded page
Once you've set up  your webform you have the option to set up how the form responds after asubmission has been made. On the your Webform's Setting page...:


If you click the 'Customize Confirmation' checkbox you can - "Configure your website's actions when a user submits a response to this webform."


  Select from the following form submit options in the menu:
  
  
  Show standard confirmation page - Displays a confirmation page that contains the information you enter in the Page body field.
  Redirect to a different page - Redirects users to the page in the Path field. You can also display a confirmation message by selecting the Show a confirmation message check box, and then entering information in the Page body field.
  Stay on the same page - Users stay on the webform page. You can also display a confirmation message by selecting the Show a confirmation message check box, and then entering information in the Page body field.
  


You probably want to select the third option...