The Oracle community is one of those web sites where I always have to use the Firefox View/Zoom option for a better reading experience. Luckily, Firefox remembers such setting on a per site basis, but I finally find it somewhat annoying having to deal with it.
If you are tired of reading small prints too, the following works for me:
In the Firefox URL bar, type: about:config
Then type Pix and open layout.css.devPixelsPerPx
Mine was set to -1. After setting this to 1.25, reading is much easier. It also makes sense if you have a larger screen. I can finally reset all the zoom options, and also re-enable "Allow pages to choose their own fonts" in my Firefox preferences. The later never really worked very well anyway.