How does SharePoint determine whether to send the "X-Download-Options:
noopen" HTTP Response header (i.e. whether to present a Save or Open
option to a user)? The following notes outline the various scenarios
through which SharePoint makes the determination to send the
“X-Download-Options: noopen” HTTP Response header. When serving a
file, SharePoint 2010 and 2013 use the following logic (from a high
level): •Check the Web Application’s Browser File Handling Property
◦If it is “Strict” then all untrusted files within the Web Application
will always include the include the “X-Download-Options: noopen”
header in the HTTP response. ◦If it is “Permissive” then SharePoint
will check the Browser File Handling Property of the list or document
library within which the file resides. This is an override of the Web
Application Browser File Handling setting:
■If the List/Document Library Browser File Handling Property is set to
“Strict” and the MIME type being requested is not on the trusted MIME
type list (i.e. the Web Application's
AllowedInlineDownloadedMimeTypes), then the HTTP Response will include
the “X-Download-Options: noopen” header.
■If the Document Library Browser File Handling Property is set to
“Permissive” then the HTTP Response will omit the “X-Download-Options”
header.
Some important additional notes:
•You cannot override the Browser File Handling Property at the
List/Document Library level to be more accommodating than at the Web
Application level. For example, if your Web Application’s Browser File
Handling property is set to “Strict” and then List/Document Library
within the Web Application is set to “Permissive”, the HTTP Response
will include the “X-Download-Options: noopen” header unless the MIME
type being served is on the trusted file list.
•You can override the Browser File Handling Property at the
List/Document Library level to be more restrictive. For example, if
your Web Application is set to “Permissive” and then set a Document
Library to “Strict”, the HTTP Response will include the
“X-Download-Options: noopen” header unless the MIME type being served
is on the trusted file list.
•For the “X-Download-Options: noopen” header to be omitted completely
one of the two scenarios must be true: ◦The MIME type being served is
on the Web Applications trusted file list, or ◦The MIME type being
served is not on the Web Applications trusted file list and the
Browser File Handling Property for both the Web Application and the
List/Document Library within which the file resides is set to
“Permissive”. •It is important to stress that the trusted file list
is unique to a Web Application. The number of trusted file lists (i.e.
AllowedInlineDownloadedMimeTypes lists) you have is equal to the
number of Web Applications you have in IIS serving SharePoint sites.
This is important to understand as if you wish to add
“application/pdf” to all trusted file lists within your SharePoint
environment, you’ll need to add it to the trusted file list for each
Web Application that serves SharePoint sites.
http://social.technet.microsoft.com/wiki/contents/articles/8073.sharepoint-2010-and-2013-browser-file-handling-deep-dive.aspx#How_does_SharePoint_determine_whether_to_send_the_X-Download-Options_noopen
now you know you can set this accordingly:
•Browse to the Central Administration site, click Manage Web
Applications under Application Management.
•Select the web application and click onGeneral Settings from the
ribbon
•Scroll down to Browser File Handling, and choose Permissive instead
of Strict.
http://support.microsoft.com/kb/2661910
changing it to permissive only works for the web root level and would require powershell script to go through sub sites or use this console app:
http://www.ride-the-bytes.com/?p=886
if your case i think it should be strict as you want the dialog box to appear!
