There are some difficulties by setting globalization of a web site. By default .Net framework use unicode. Therefore it is not necessary to set this. If you have to use different encoding you can set this in web.config:
<globalization fileEncoding="utf-8" requestEncoding="utf-8" responseEncoding="utf-8" culture="bg-BG" uiCulture="bg-BG">
Check the following links for more information:
And here is a explanation of the Visual Studio behavior. VS may cause some problems if you don't know these issues.
The last link helped me to decide my problem. I had to save all my files with utf-8 encoding to get Cyrillic encoded response.