Disallow units for zero lengths.


a { top: 0px; }
/**      ↑↑
 * This zero and this type of length unit */

Lengths refer to distance measurements. A length is a dimension, which is a number immediately followed by a unit identifier. However, for zero lengths the unit identifier is optional. The length units are: em, ex, ch, vw, vh, cm, mm, in, pt, pc, px, rem, vmin, and vmax.

长度 指的是距离的测量值。长度是一种维度,用 数字 表示,后面紧跟着一个 单位标识符。然而,对于长度为 0 的情况,单位标识符是可选的。长度单位包括:emexchvwvhcmmminptpcpxremvminvmax



The following patterns are considered warnings:


a { top: 0px }
a { top: 0.000em }

The following patterns are not considered warnings:


a { top: 0 } /* no unit */
a { transition-delay: 0s; } /* dimension */
a { top: 2in; }
a { top: 1.001vh }