This is really nice, it works well and it doesn't make my PC's fan sound like jet plane taking off, so that means it's likely safe.

Thank you :-)

It would be nice to be able to:

1. Set / toggle it for ALL websites
2. Toggle it on/off with a keyboard shortcut

Love it - a very useful addon if you have a wide screen. Should add the ability to use hotkeys to activate!! The option isn't present in the addon settings nor via firefox settings. Would be a great feature.

This seems redundant, why don't you just adjust the size of the window? I was hoping it would do the opposite.

Almost perfect! Allows to to enable it on specific websites with a specific width for each. The only weird issue is that when you accidentally click in the empty space created by the add-on, for some reason it selects all the text in the page...