css线性渐变兼容
background: linear-gradient(top, rgba(54, 77, 127, 0.8), rgba(54, 77, 127, 0.8));
background: -moz-linear-gradient(top, rgba(54, 77, 127, 0.8), rgba(54, 77, 127, 0.8)); /*Firefox*/
/*参数：top、bottom垂直，left、right水平*/
background: -ms-linear-gradient(top, rgba(54, 77, 127, 0.8), rgba(54, 77, 127, 0.8));
background:-o-linear-gradient(top, rgba(54, 77, 127, 0.8), rgba(54, 77, 127, 0.8)); /*opera*/
/*参数：top、bottom垂直，left、right水平*/
background:-webkit-gradient(linear, 0 0, 0 bottom, from(rgba(54, 77, 127, 0.8)), to(rgba(54, 77, 127, 0.8))); /*Chrome、Safari*/
/*参数：linear线性， x1 x2, x3 x4 x1与x3相同时垂直，x2与x4相同时水平 from起始颜色 to结束颜色*/
