Sigh... You'd think people would know this by now. What does it even mean to be a "web developer" if you don't know the difference between pixels and text size?

Sigh... You'd think people would know this by now. What does it even mean to be a "web developer" if you don't know the difference between pixels and text size? It seems like such a fundamental thing, like a decorator knowing how to calculate how much paint is needed for a job. But no... now we have web browsers where a pixel isn't even a pixel, it's 4 pixels, on a "HiDPI" display...