This is an intended consequence of bug 1423709. The initial zoom level now matches Chrome's behaviour. The page appears to be zoomed out more than it should be, because most of the contents are a fixed width, but there is content further down which is wider, and we are basing the zoom on the total width. Perhaps the website could be better constructed, so that posts with wide content are horizontally scrollable instead of having visible overflow. However, that's not a browser issue. (You're welcome to [file an issue against the planet.mozilla.org site](https://bugzilla.mozilla.org/enter_bug.cgi?product=Websites&component=planet.mozilla.org) about that.)
Bug 1521359 Comment 5 Edit History
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This is an intended consequence of bug 1423709. The initial zoom level now matches Chrome's behaviour. The page appears to be zoomed out more than it should be, because most of the contents are a fixed width, but there is content further down which is wider, and we are basing the zoom on the total width. Perhaps the website could be better constructed, so that posts with wide content are wrapped in a horizontally scrollable div, rather than widening the entire document. However, that's not a browser issue. (You're welcome to [file an issue against the planet.mozilla.org site](https://bugzilla.mozilla.org/enter_bug.cgi?product=Websites&component=planet.mozilla.org) about that.)