Usually the only exception to your setting to divert new windows to new tabs instead is when a site uses a script and specifies that a window should have certain attributes, such as a particular size.

Does the type of attachment matter? I tested two files but it might depend on the type of content and how Firefox is set to handle it:

• JPG: "View" opened a new tab, "Download" showed the Open/Save/Cancel dialog
• PDF: "View" opened a Google Drive viewer in a new tab, "Download" showed the Open/Save/Cancel dialog

What did you set in about:config? Was it one of these?

(A) browser.link.open_newwindow

3 = divert new window to a new tab (default) (checked*)
2 = allow link to open a new window (unchecked*)
1 = force new window into same tab

* First checkbox in Options > Tabs

(B) browser.link.open_newwindow.restriction

0 = open_newwindow preference honored for all new windows
2 = open_newwindow preference honored for all new windows except script windows with features (default)
1 = open_newwindow preference ignored completely (same effect as open_newwindow=2) (new windows open in new windows even if you checked that you want them in tabs instead)

By default, popups that specify a particular window size or turn off certain window features will appear in a new window. If you set this preference to 0 then all popups are forced to a new tab.

this thread's mozilla link itself from gmail opened in a new window. the key pain point here is that only this specific system/browser doesn't behave as expected as the rest.

browser.link.open_newwindow = 3 browser.link.open_newwindow.restriction = 1

options had been set to open window in tabs.

i really think its one of the plugin, as that's the only thing differ this system to others, but it doesn't make sense when all plugins are disabled yet it is still broken.

Try resetting this one to the default value of 2, because currently it is set to overrides the dialog preference:

browser.link.open_newwindow.restriction

magic! that appears to be the culprit... i guess "(same effect as open_newwindow=2)" was lying to me.

thanks!

Or I wrote it unclearly. If you look up 2 under the first preference, that's what you get if you uncheck the box in your tab preferences.

ahhh, i get you now... yeah, that needs some clean up.

Hopefully the edit makes it clearer for the next people who try to puzzle out what I was saying. :-)

See also:

• http://kb.mozillazine.org/browser.link.open_newwindow
• http://kb.mozillazine.org/browser.link.open_newwindow.restriction