Haaalp! Everything's Magnified!

[Babar]

For the last couple of weeks (possibly after I updated firefox), everything's been magnified in the browser.
When I googled around a bit, it seems that some new update of firefox dynamically changes the size of the stuff on the page depending on your monitor, which to me seems like a very horrible idea, but I guess I wouldn't mind it so much for text (although it'd take getting used to on my usually visited sites), but it does it for images as well, even when I open JUST the image in a new browser tab, which I really don't understand.
I keep my non-widescreen CRT monitor's resolution at 1280x1024, which may seem low, but I am happy with it. However, images that are even just 750 pixels tall are required to be scaled down and I need to click the magnifying glass to view them, at which point I have to use the scrollbars to view them!
I know I am not imagining it, because when I copy the image and paste it into Paint, it shows up smaller.

I haven't had so much of a problem on these forums, possibly because I have gifs and pngs to magnify using nearest neighbour(?) and how most pixel-level art here is posted using tags or something (or possibly because I haven't noticed it yet :O), but it is annoying me on most of the rest of the web, and I'm second-guessing myself as to whether everything just got bigger, or it is normal, or what.

Following instructions on some mozilla help thing (where someone else posted a similar problem), I installed the NoSquint add-on, but while that helps somewhat (but not really) by setting a default zoom level for everything or for specific websites, I'm mostly setting the size by guesswork, and Firefox STILL expands it when I open a picture in a separate tab (NoSquint gives the message that the zoom level is N/A for that page).

So...mozilla's own help thing has been kinda unhelpful, but I hope someone here might have a solution for this?

Thanks in advance!

[DoorKnobHandle]

You tried CTRL+0, right?

EDIT: On second thought, it sounds like you probably did, so disregard, sorry!

[Babar]

Yup. No effect. In fact, I'm having to do Ctrl+- on most pages or images.

[selmiak]

CTRL+Mousewheel down?

[Babar]

Ctrl+Mousewheel down reduces the size of stuff, yeah, but that is only a temporary solution, I'm hoping there is some way I can set it so that no initial magnification at all occurs. I don't want to have to do Ctrl+Mousewheel down or Ctrl+- every time I open a new tab.

I had also set Zoom Text Only in the View->Zoom menu, which had no effect (on the text OR the images), and after installing NoSquint I also set it to zoom text only (it had such an option as well), but while that did modify the zoom for text (I currently have it set to show everything at 80% of what Firefox renders it, which I chose through pure guesswork) it still showed magnified images in the page, and setting it to text only OR text and images it didn't help for images alone at all.

[Esseb]

Have you tried changing layout.css.devPixelsPerPx as described on https://support.mozilla.org/en-US/questions/963710?

[Babar]

I think that worked, thanks for that! Now everything in the interface (File, Edit, etc.) is tiny, but I'll live with that, as long as the content is the size it is meant to be. It boggles the mind that they'd make such a thing adjustable.