Thank you, I have tried again and also changed the style.css.
I now see the larger font on this page: http://www.dietzcoaching.nl/weblog/ (the blog page overview with short introductions to every blog), that’s great. But when I open a single blog (like this one http://www.dietzcoaching.nl/is-baas-huis-grenzen-aangeven/), the font is still small. Is it possible to enlarge the font in each single blog?
I’m sorry for asking all these questions, I’m really happy with your help!