Thin text of menu in Firefox

Hi Caroline,

I am having issues with the readability of the menu in Firefox.
See http://www.schoolontwerpen.nl

Some months ago you fixed the issue, in this post:
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http://wordpress.org/support/topic/darken-top-menu-colors?replies=12

@bonbonthief, the fix I implemented was adding -webkit-text-stroke: .35px; /* Hack to fix thin text in Windows */ in style.css, on any elements where the font-family was set to Quicksand, since that seems to be the problematic font. This appears to fix it for me in webkit-based Windows browsers, but YMMV.
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However, Firefox still has the same issue.
Any fixes?
Or can I change some code anywhere myself?

thanks, Bastienne