It’s an encoding problem. You have to set the correct encoding in the HTML head via meta tag:
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
Replace “ISO-8859-1” with whatever your encoding is (e.g. ‘UTF-8’). You must find out what encoding your HTML files are. If you’re on an Unix system, just type file file.html and it should show you the encoding. If this is not possible, you should be able to find out somewhere what encoding your editor produces.