*{ 
    margin:0;padding:0;  outline: 0;  vertical-align: baseline; 
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
    -webkit-tap-highlight-color: transparent;
}
html,body{ 
    color:#000; 
    background:#fff; 
    font:12px/22px Verdana,Arial,sans-serif,"Times New Roman",思源宋体; 
    width:100%;
    overflow: hidden;
}
input,select,button{ 
     font-size:100%;
     outline:0;
     vertical-align:middle;
     -webkit-appearance: none;
 }
button{
    border: 0;
    background-clip: padding-box;
}
table {
    border-collapse:collapse;
    border-spacing:0;
}
ol,ul,li { list-style:none;}
/* 定义图片边框，当图片作为链接内容被填充时，会有默认边框出现，重定义掉 */
img{ 
     border:none;
     vertical-align:baseline;
}
a, a:link, a:visited{
     color:#000;
     text-decoration:none;
}
a:hover{ 
    color:#000; 
    text-decoration:underline;
}
/* 标签属性，textarea,input 强制输入时内容超出时换行，打断 */
textarea,input{ 
    word-wrap:break-word; 
    word-break:break-all; 
} 
span,p,div{ 
    word-wrap:break-word;
} 
.lf{ float:left; }
.rt{ float:right; }
.clearfix{ content: ''; display: block; clear: both; }

• 普通适配：

@media screen and (min-width:321px) and (max-width:375px){
    html{font-size:11px}
}
@media screen and (min-width:376px) and (max-width:414px){
    html{font-size:12px}
}
@media screen and (min-width:415px) and (max-width:639px){
    html{font-size:15px}
}
@media screen and (min-width:640px) and (max-width:719px){
    html{font-size:20px}
}
@media screen and (min-width:720px) and (max-width:749px){
    html{font-size:22.5px}
}
@media screen and (min-width:750px) and (max-width:799px){
    html{font-size:23.5px}
}
@media screen and (min-width:800px){
    html{font-size:25px}
}

• 精确适配:
  rem为单位，实现包括字体大小、元素间距等的自适应，则需要body前加上几行js。因为pc谷歌浏览器调试不支持小于12px，网上很多是以屏幕宽/37，例如：iphone6为例1rem=10px,此处改为/18.75，1rem为20px，iphone6plus为23.52px

var html = document.getElementsByTagName("html")[0];
var w = document.documentElement.clientWidth || document.body.clientWidth;
html.style.fontSize = w/18.75 +"px";