My websites and UI have suddenly become huge. How can I get them back to a normal, smaller size?

Question

Yesterday all of a sudden my webpages and UI appeared to be magnified. While I can zoom out on websites, I cannot find any option to adjust the size of the UI.
I noticed that Firefox 22 (which I am running) has a new feature: "Windows: Firefox now follows display scaling options to render text larger on high-res displays". Is it possible to adjust how Firefox responds to the display scaling options perhaps?
''07-27-13 - moderator locked this due to the length of this two month old thread - please post in one of the other threads discussing this issue''

Answer 1

WARNING!!!
This is extremely bad advice! =(
I tried 0.05 and and that broke my FF 22 installation irreversibly, since all text became unreadable.
==Please Note==
This is explained in the next post but is not visible from all pages so I am adding it in directly
''The steps have a resolution of 0.05 (0.95 0.9 0.85 0.8)
Of course you shouldn't go back all the way to 0.05 or you would have to edit the prefs.js file ''
<br />_{A forum moderator ~J99}
Then don't post "0.05" as a value, when people ask what to put in that variable.
Of course people will try it.
And of course nobody would expect 0.05 to be '''smaller '''than both -1 '''and '''1, on an unknown scale.
<br />_MatsSvensson
Fortunately i could go back to version 21.
I spent a couple of hours googling this problem, and trying various workarounds, which the web is now overflowing with.
But it seems impossible to completely get FF22 not looking like shit and distorting the crap out of all websites.
Now i have turned off updating, and will stick with 21 until this idiotic garbage is removed from Firefox.
And besides, even IF i could have applied some hack, SO WHAT?
99.99999% of all users wont be able to, or wont bother to do it, or wont know its even an option, which means we then have to start designing websites that both look good on non-swollen AND swollen (Firefox) browsers!
Congratulation to making FF the new IE6.
OBVI-FU**ING-OUSLY its NOT a good idea to start telling people to apply various hacks to work around this, since this will fragment the way the same sites look in the same browsers (even more so).
The correct response is to grasp that this "feature" is broken and remove it, or fix it, an stop rolling out the broken version before it does even more damage.
How the F can they roll out something THIS epically broken?
I have found posts dating back months, from people using beta versions, who reported exactly this problem.
And STILL it was rolled out?