Same issue here, Firefox fonts appear very large on certain sites and sometimes only on certain sections of a site, while others appear normal. Changing about:config setting layout.css.dpi to 96 appears to correct the problem.
If this is of any use:
$ xdpyinfo
screen #0:
dimensions: 1680x1050 pixels (331x201 millimeters)
resolution: 129x133 dots per inch
Same issue here, Firefox fonts appear very large on certain sites and sometimes only on certain sections of a site, while others appear normal. Changing about:config setting layout.css.dpi to 96 appears to correct the problem.
If this is of any use:
$ xdpyinfo
screen #0:
dimensions: 1680x1050 pixels (331x201 millimeters)
resolution: 129x133 dots per inch