Specify a character set for your HTML pages.

This tells the browser how to display non-ASCII characters and how to interpret values that forms return to the server.
See the w3schools website for common character sets. An example from Google:

<html>
  <head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
</html>
Copyright Donald Horrell 2012, 2013. All rights reserved