/* mycss.css */

#container {
    width: 500px;
    /* width: 70%; */
    margin: 0 auto;
}

#header {
    background-color: red;
}
#main {
    background-color: blue;
    overflow: hidden;
}
#footer {
    background-color: green;
}

#left {
    background-color: pink;
    float: left;
    width: 200px;
}
#right {
    background-color: purple;
    margin-left: 300px;
}