To ensure it will always work, for this specific example, you can replace the non ASCII characters using Html entities, like this: Bibliothèque. But this is not always practical in general.

Otherwise, there are other various ways to make it work:

• use byte order mark encoding (sometimes called 'signature', or BOM, by editors) and save the file as UTF-8
• add a META character encoding to your html file.
• define what HTTP headers will be sent to the client using the globalization element in the application web.config (responseEncoding, etc.)
• define what HTTP headers will be sent to the client using the ASP.NET @page directive

The best is to make sure all this is consistent in your application. UTF-8 support is now widespread, so it's a good choice as the encoding.

An interesting article on the encoding subject :The Definitive Guide to Web Character Encoding