Css验证器给出了不允许的错误

Question

我正在使用validator.w3.org并出现错误。为什么这个错误发生在 css？任何人都有建议去除这个错误。

Line 1, Column 1: character "*" not allowed in prolog 

Line 20, Column 2: character "m" not allowed in prolog 
**m**argin: 20px 0 0 20px; 

Line 31, Column 2: character "b" not allowed in prolog 
**b**ackground-image: -webkit-gradient(

Line 57, Column 1: character "{" not allowed in prolog 

Line 113, Column 2: character "w" not allowed in prolog 
width: 90px; 

Line 133, Column 2: this is not an SGML document 

Answer 1

validator.w3.org是标记文档（XML，HTML等）的一个验证。

验证CSS使用https://jigsaw.w3.org/css-validator/。