I am a bit puzzled with the fonts for Twenty Thirteen, with 2 problems that I have been unable to solve up to now (after hours of research...). They are not limited to my website and are also present on all other websites using 2013 that I checked.
1. It seems that Chrome for desktop loads the font "Source sans pro" with a very annoying letter-spacing that impairs readability a lot compared to the great rendering on Firefox.
Note that I encounter this problem only on laptop, the rendering on Chrome for iPhone for example, is great.
2. It seems that Firefox doesn't load the "Bitter" font, all titles are rendered in Georgia, which makes the template's appearance quite different from other browsers.
Thank you for your support, and hopefully solutions for these problems.