If you need to increase or decrease the size of fonts and other elements in the user interface and web pages then

Increase the String pref layout.css.devPixelsPerPx from 1.0 to 2.0 in 0.1 (or smaller) steps to see what works best.

In current Firefox versions this pref is a String value parsed to a float and allows to fine tune the dimensions of all elements (user interface and web pages) more precisely.

To open the about:config page, type about:config in the location (address) bar and press the "Enter" key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.

• http://kb.mozillazine.org/about%3Aconfig

Got there....not sure exactly what to do....and of course.....I do not want to change a setting that does not need changing.....

I want to the change the address/tool bar font size to be larger.....

Please advise.

Mark

Once you get to "about.config" enter "pixels" in the search box at the top of the list. That will bring up the line you want to change, (layout.css.devPixelsPerPx.) Change the value from 1.0 to whatever suits you.