Download launches blank window
From MozillaZine Knowledge Base
When downloading a file you may find that Firefox launches an unwanted blank window. This occurs because the webmaster has specified that the download should start in a new blank window even though this was probably not their intention. This is a known issue[1] and hopefully Firefox will handle these cases better in future.
You can fix the problem by downloading the Disable Targets for Downloads extension.
Webmasters can fix the problem on their site by removing target=_blank or window.open from the download links.
