* {
    margin: 0;
    padding: 0;
}
h3 {
    width: 960px;
    height: 50px;
    background: #ccc;
    color: #000;
    text-align: center;
    line-height: 50px;
    margin-bottom: 10px;
}
#img1 {
    width: 960px;
    margin: 24px auto 38px;
    display: block;
}
#img2,#img3 {
    display: none;
}
.main {
    width: 960px;
    margin: 10px auto;
    overflow: hidden;
}

.left {
    width: 630px;
    height: 300px;
    background: #f00;
    float: left;
}
.right {
    width: 320px;
    height: 300px;
    background: #00f;
    float: right;
}
@media screen and (max-width:480px) {
    #img1,#img2 {
        display: none;
    }
    #img3 {
        width: 100%;
        display: block;
    }
    .main {
        width: 100%;
    }
    .left {
        width: 100%;
    }
    .right {
        width: 100%;
    }
    h3 {
        width: 100%;
    }
}
@media screen and (min-width:960px) {
    #img1,#img3 {
        display: none;
    }
    #img2 {
        width: 100%;
        display: block;
    }
    .main {
        width: 100%;
    }
    .left {
        width: 63%;
    }
    .right {
        width: 32%;
    }
    h3 {
        width: 100%;
    }
}