Is there a specific rule the default WordPress themes follow for CSS units?
I see em's on some font sizes and rems on others and px on certain places.
Referred the following links but I couldn't find the actual reference to the rule they use for their CSS units: why does twenty eleven theme mix up the css measurement units? Why do Wordpress default themes specify fonts in so many places?
Edit: By rule, I meant, for eg: Always follow the unit system of - px for borders, em for spacing etc