I didn't see where you said which browser you are using - I use (shudder) IE.   I also run into difficulties with those-who-think-for-you, deciding which mixed set of four font sizes they thought _so_ nice.   My solution is to ignore them.

In IE select Tools / Internet Options... / Accessibility... (button on lower-right), and then with _great_ satisfaction check "Ignore font sizes specified on web pages".   I actually run like this all the time, though you might just want to do it for a few (self-selected, in a way) sites.

I got over any possible negative associations with using an "Accessibility" feature long ago, figuring I'm just counter-balancing the "inaccessibility" features the web developers indulged in.