But if we do not want that at startup Firefox retains the settings adjusted to the previous session we can install following addon.
https://addons.mozilla.org/en-US/firefox/addon/default-fullzoom-level/
here you can find more technical details:
About this Add-on
1.This extension can change Default FullZoom Level.This extension is useful in the case of a high-definition display.
2. The zoom mode is restored every domain name or tab as well as the zoom level.
3. In the case of a local file, you can set whether zoom every file or every folder.
4. Two toolbar buttons are provided.
"A":Text Zoom BUtton.
"P":Full Zoom Button.
Left, middle, right button click will enlarge, reset and reduce page or text respectively.
Wheel button rotation will enlarge and reduce them.
And Shift+right click show up the option dialog.
5.Indicate Zoom level in Statusbar.
Left click : popup zoom level list
Middle click: reset zoom level
Right click: toggle zoom mode.
6. Keyboard shortcut:
TextZoom reduce :accel+ <(comma)
TextZoom enlarge :accel+>
Fullzoom reduce : default(accel+-)
Fullzoom reset : default(accel+0)
Fullzoom enlarge : default(accel++)
Where, An accel key may be a crtl key in Windows's keyboard.
If you want to ask something about this, please post it to the following forum.
http://forums.mozillazine.org/viewtopic.php?t=659681