How to replace all www fonts in Firefox 29 via userContent.css with preferred ones?

Question

Fonts

Firework!
Challenge: Replace fonts with Verdana in web page content.
OS: Windows 7/64
Browser: Firefox 29.0.1
Attempt:
Created profile\chrome\userContent.css

@font-face { font-family: 'serif'; src: local('Verdana'); }
@font-face { font-family: 'bold serif'; src: local('Verdana'); }
@font-face { font-family: 'sans-serif'; src: local('Verdana'); }

@font-face { font-family: 'Arial'; src: local('Verdana'); }
@font-face { font-family: 'Georgia'; src: local('Verdana'); }
@font-face { font-family: 'Open Sans'; src: local('Verdana'); }
@font-face { font-family: 'PT Sans'; src: local('Verdana'); }
@font-face { font-family: 'Tahoma'; src: local('Verdana'); }
@font-face { font-family: 'Trebuchet MS'; src: local('Verdana'); }

Problem: Only some of the described fonts are
replaced by Verdana : Arial, Georgia, Tahoma... Families/fonts are NOT replaced: "bold serif", "PT Sans", "Open Sans", "sans", "italic sans" (and some others), and it hurts my eyes. Question: How to reliably replace all fonts with Verdana? Constraints: I need to differentiate monospaced fonts and replace them with Lucida Console. You can not replace ALL fonts with Verdana due to the newfangled fad to use Webdings and Wingdings. Thank you!

Answer 1

Designers curse you)

Answer 2

!important?

Answer 3

Some of the fonts, like "PT Sans", as I understand it, are downloadable. And they are not killed in the way described in the question.
gfx.downloadable_fonts.enabled=false disables downloading fonts, which partially solves the problem. But not completely.