Today I’ve worked on a generic handler that recovers file from else where, than it sends the file to client browser.
When you write a generic handler it is important to specify the contentType before complete the response.
There are many mime type availables:
image/png, text/plain etc.
But if you don’t know which mime type use I suggest you to use this one:
context.Response.ContentType = "application/octet-stream"