Quite often, vendors pass images or PDFs to customers using the binary contents of the file. To make it more secure, they convert the binary contents to a Base64 string. A full explanation about Base64 encoding can be found at Wikipedia here . Anyway
Read More...
Read the complete post at http://weblogs.asp.net/jgaylord/archive/2007/10/10/writing-a-base64-string-to-the-file-system-or-browser.aspx