Funkcionalnosć toś togo sedła se pśez wótwardowańske źěła wobgranicujo, kótarež maju wašo dožywjenje pólěpšyś. Jolic nastawk waš problem njerozwězujo a cośo pšašanje stajiś, wobrośćo se na našo zgromoźeństwo pomocy, kótarež na to caka, wam na @FirefoxSupport na Twitter a /r/firefox na Reddit pomagaś.

Pomoc pśepytaś

Glědajśo se wobšudy pomocy. Njenapominajomy was nigda, telefonowy numer zawołaś, SMS pósłaś abo wósobinske informacije pśeraźiś. Pšosym dajśo suspektnu aktiwitu z pomocu nastajenja „Znjewužywanje k wěsći daś“ k wěsći.

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Scripts may not close windows that were not opened by script.

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The error in the question appears when responding to an outlook junk/not junk email. In this case not a junk email which opened this tab; https://outlook.live.com/owa/SvmFeedback.aspx?pt=0&kv=1&ts=131604366339430333&iv=uupoatqVORKSCpilJUzdQw%7e%7e&authKey=uusDUh9KkkiRjLzVV90bwHwBjr0It6_qZO4U-XZ3hKzvHSV4cVmPKjNa__4b9NtYttqBzKxvF2ldKRkjJnrpxFOQf_qQvnLmxkP5Jja0FNEalnLUVSk_7cOJ_S8-3LYso0SX0pu1gA8eb9ALL2Zwr2TOruajdxnEHtWAtwwnA0c%7e&hmac=8AjhlchmP08rvdHJ9T6ZREBLIKC25MqE1IUJfp91dJ8%7e The was one button "close" which did not work. See attached screen print.
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Wšykne wótegrona (1)

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Hi SteveRiley, how was that tab opened in the first place? If the tab was opened by a script in the mailbox using the window.open() script method, then the Close button should work. However, if it was opened in some other way, then you'll need to close the tab manually (e.g., middle-click the tab or Ctrl+w or one of the other methods).