*{margin:0;padding:0}
body{color:black;font-size:18px;font-family:arial;background:orange;}
#box{margin:50px auto;width:500px;height:600px;border:4px solid black;}
header{width:100%;height:100px;background:blue;}
#content{width:100%;height:400px;}
footer{width:100%;height:100px;background:green;}


/**    layout 1    **/
#layout .left{width:50%;height:400px;background:cyan;float:left;}
#layout .right{width:50%;height:400px;background:red;float:left;}

/**    layout 2    **/



/**    layout 3    **/