Imagine a CGI script that does not work as expected and makes the Apache web server respond with a 500 Internal Server Error. At least in this case (maybe other 500, too) the server gets the Content-Type: header wrong: Result: HTTP/1.1 500 Internal Server Error ... Content-Type: text/x-python Expected: ... Content-Type: text/html It seems that the web server sets the Content-Type to the mime-type of the CGI source file. Even "ErrorDocument ..." with or without "ForceType text/html" have no influence. Because of this, Firefox and other browsers offer a download dialog instead of displaying the error...
Long overdue to apply the simple fix. *** This bug has been marked as a duplicate of 39710 ***