The file encoding you use limits the characters that you can use in your DSP (including the data inserted into your DSP using %VALUE% statements) to those in the character set of the encoding you choose. It also limits any translated versions of the DSPs to the same character set. Generally it is a good idea to use the UTF-8 (Unicode) encoding, since Unicode supports nearly all of the characters in all of the world's languages. You will not lose any data if you choose to save your DSP in UTF-8; any data entered into a form will be properly interpreted by Integration Server.
The encoding you choose also applies to any localized (translated) versions of the DSP that you create, so you should choose a character encoding that supports all of the languages for which you will create localized DSPs. For details, see
DSPs and Output Templates in Different
Languages.