Judging by the jagginess and the low resolution of your screen, I'd wager you're using one of the laptops with an integrated GPU that's using an older version of the drivers that's on the Firefox GPU blacklist. This is usually because the laptop maker doesn't bother to update the graphics drivers much, if at all, and doesn't get the improved ones from Intel/AMD/etc. These outdated and buggy graphics drivers cause apps that use hardware acceleration to crash, so Firefox is running with it off on your laptop. Mozilla maintains a blacklist of known bad versions of graphics drivers and will automatically disable hardware acceleration on those machines so that it won't crash. With it off, web pages won't look as good and web fonts won't be as smooth.
Neither my laptop nor my desktop suffer this issue with Firefox, Chrome, IE, etc.
