Xenforo 2.1 how to change theme size to 125% ?

[DRIVER1ksa]

i try this

body {
zoom: 1.25;
}

it work but All drop-down menu and pop-up window are in the wrong places.

 

[Splicho]

i try this

body {
zoom: 1.25;
}

it work but All drop-down menu and pop-up window are in the wrong places.

DRIVER1ksaOf course. Because it scales all elements by 1.25, as well as dropdowns.
Dropdowns have mostly relative position to the viewport, that's why they are out of place when scaled.

Why do you want to scale everything ? That's usually a really bad approach, especially with applying that to the body.