linear-gradient
background: -moz-linear-gradient(top, rgba(255,255,255,0), rgba(255,255,255,.2) 50%, rgba(255,255,255,0));
? background: -webkit-linear-gradient(top, rgba(255,255,255,0), rgba(255,255,255,.2) 50%, rgba(255,255,255,0));
? background: -o-linear-gradient(top, rgba(255,255,255,0), rgba(255,255,255,.2) 50%, rgba(255,255,255,0));
? background: -ms-linear-gradient(top, rgba(255,255,255,0), rgba(255,255,255,.2) 50%, rgba(255,255,255,0));
? background: linear-gradient(top, rgba(255,255,255,0), rgba(255,255,255,.2) 50%, rgba(255,255,255,0));
請問：這里的參數(shù)50%是什么含義？
2020-01-31
50%為透明參數(shù)，取值在0和1直接，不可為負(fù)值哦?