On a whim. I checked the top 50 websites according to Alexa.com. And 46 out of 50 use sans serif fonts on their website. The four that don’t:
nytimes.com
imdb.com
washingtonpost.com
digitalpoint.com
Notice two of those are online newspapers… which of course would use a serif font. The other two? I have no idea why. But the message it’s sending is clear. All the people with the money to do the research are using san serif fonts. Take notice.

