Child pixels / parent pixels = child ems

子元素像素值/父元素像素值=子元素ems

So , your site cannot have a fixed width with pixels . Its much better to use percentage and ems .

所以，你的网站不该用像素值来固定宽度，用百分比和ems会更好。

I never been a fan of ems in css files , but sometimes you have to deal with it .

我对css文件中的ems一点也不喜欢，但有时你却不得不处理它。

Ems : I am wondering why the isotope ratios in the ancient meteorites is not considered to be those of the primordial cloud in which they formed .

ems:我很好奇为什么古代陨石的同位素比率和形成它们的原始云有什么不同？