I have used the same css and js for all the browsers. There is no browser specific coding done. Also i tried adding the normalization code. But this did not help. i read this: https://support.mozilla.org/en-US/questions/962979 . Now i know that changing the value of 'layout.css.devPixelsPerPx' manually will help. But this will solve the problem only in that particular system. I have many users accessing my site from many systems. How do i make sure they have the same look and feel without going to about:config and changing the value of 'layout.css.devPixelsPerPx' manually. PLease help. Thanks