Firefox automatically enlarges the page problem

This problem recently just play clear, high-split screen people often zoom to 125% or other, the result of Firefox font page What will also appear larger, only the Firefox each page zoom to 80% will show normal, this problem is really annoying, but now solved.
Open Firefox, enter about:config in the URL bar, and then search layout.css.devPixelsPerPx, we can see the default value is-1.0, right-click Change, 1.0 to 1.0, perfect solve the problem

Firefox automatically enlarges the page problem