Thanks to Jarrad, this extension is very useful.
It has only one problem: compatibility with new Firefox for android. I added this extension to new Firefox, but it didn't work :(

Used to work, but doesn't seem to do anything these days.

Breaks some sites:
1) http://forum.mozilla-russia.org - spoilers in topics don't work.
2) Chrome addons webpages (for example, https://chrome.google.com/webstore/detail/fit-to-width/dfdmbpdbpocelpgahddghhkomnefchkl )

Хорошо работает на большинстве страниц, проблема с горизонтальной полосой прокрутки становится редкой. Подобные возможности должны быть встроены в браузер.
Но ломает некоторые сайты (см. выше).

Just a lifesaver!
This functionality, however, should be in Firefox by default.

Works great for me. Helps me read Oracle JavaDoc conveniently. Thanks!

Superb extension to read anything

This is inferior compared to the other for to width add on that is no longer available. In this version it does everything automatically so basically if you zoom in on a page that already is good but you just want to see the letters a little bit larger it'll try to resize the entire page. This ends up throwing off the entire page and you actually can't even lose your place of where you're eating. The other version which I cannot find currently was where you tap to adjust the font to fit the screen and that worked really well because it would allow you to manage which things get adjusted instead of the entire page automatically

Cool. Its working on my android phone.

Doesn't work at all :(

Doesn't work for me on my Samsung 7

this is an essential addon!
Thank you!

Works on most site but why don't it work on reddit?

Doesn't work. Tried to word wrap the view-source of a web page