You have this fairly big script being loaded at the top that starts like this:
When I look at your site, it very briefly flashes with raw, unstyled HTML. I think this script is causing that. And chance of moving it to the end of the file instead of the header. If it is fixing up fonts, at least it would do it for mostly styled content rather that giving that unstyled flash.
And, by the way, the site makes me want t come and visit!