I was trying to display some Flash SWF files within a SharePoint 2010 WebPart. The SWF files were stored in a document library, but when the page was loaded, only a blank, white space was displayed.

After much frustration and searching, I came across mention of a setting in Central Admin.

Apparently, SharePoint adds headers to certain file types to force the browser to open a save dialog instead allowing automatic execution of content. This results in Flash content not displaying as expected.

In order to prevent SharePoint from adding these extra response headers, go to Central Admin -> Manage Web Applications. Then select your web application, and go to General Settings. You should be prompted with the following dialog:

Set it to "Permissive" and enjoy..