In .NET when I get a response stream from the server what type of encoding type should I use?-Collection of common programming errors

It depends on what you’re expecting from the server. In the case of HTML (which seems to be your expectation), ASCII works 99% of the time for English-language pages, and should allow you to decode all HTML elements regardless. However, one of the first things you should do is read any “meta” tags in the head element of the document; these will specify the encoding of text in the body. Usually, if that isn’t ASCII it’s UTF-8, which is backwards-compatible to ASCII (but will show some weird characters for 2-byte and 4-byte character codes).