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Happpens on other sites too...

Why are those bars from the page footer floating up into the middle of the page? So strange.

{Nerdy style notes} The div[id="fbar"] has position:absolute set, but the bottom:0 rule should glue it to the bottom of the page. Is there a preference that could change that?!

Could you check for modified layout.css preferences -- here's how:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.

(2) In the search box in the page, type or paste layout.css and pause while the list is filtered

Firefox will list over a page of rows.

(3) Check the box on the right side for "Show only modified preferences"

Is there anything still listed?

(Based on mine, disabling thin scroll bars by setting layout.css.scrollbar-width-thin.disabled to true doesn't cause this problem.)

Try to clear the Google cookies via the padlock icon in case you participate in some Google experiment.