是否有任何实际的理由使用“em”而不是“pt”字体大小单位？

One CSS rule I have learned is that you should use the relative "em" font-size unit instead of the absolute "pt". The general idea is to set the font-size in your body tag to e.g. "94%" and then set all other elements with an "em" size like this. The reasoning is:One CSS rule I have learned is that you should