This was redundant and doesn't do what I hoped. I hoped it would widen those pages that unnecessarily narrow the text like the pre-WebEX "Dr. Body Narrow" did.
Instead of this, just use "Restore" aka "Windowed mode" instead of maximizing the size of the browser window and adjust the size of the window to the size you want.

It reduces the width of the page, but it doesn't listen to custom value anymore - page stays the same width as the default value of 960px.

Debería mantenerse el cambio de ancho al navegar a través del links y no tener que apretar cada vez.

Además la barra de desplazamiento tambien deberia situarse en el ancho indicado.

Y estaría de lujo si dejase escoger el color de los bordes añadidos, sobretodo para poner un tema oscuro.