html {
    display: flex;
    flex-direction: column;
    height:100%;
}

body {
    flex:1;
    display:flex;
    flex-direction:column;
}
/*------l_01 布局（上、中、下）-------*/
/*
    <div class="l_01_top"></div>
    <div class="l_01_middle"></div>
    <div class="l_01_bottom"></div>
    */
.l_01_top{height: 80px;}
.l_01_middle{flex:1;}
.l_01_bottom{height: 50px;}




/*------l_02 布局（上、左侧菜单，右侧内容、下）-------*/
/*
    <div class="l_02_top"></div>
    <div class="l_02_middle">
        <div class="l_02_leftMenu"></div>
        <div class="l_02_rightContent"></div>
    </div>
    <div class="l_02_bottom"></div>
    */
.l_02_top{height: 80px;}
.l_02_middle { width: 1200px; margin: 0 auto; overflow: hidden; display: flex; }
.l_02_leftMenu{width: 220px;float:left;margin-right: 30px;}
.l_02_rightContent{width: 950px;float:right;}
.l_02_bottom{height: 50px;}