body
{
    margin: 0;
    padding: 0;
    background: url(Chemical_background.jpg) no-repeat center center fixed;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover; 
    /* floralwhite; lightgoldenrodyellow */
    font-family: Arial, Helvetica, sans-serif;
}
#header
{
    text-align: center;
    
}
#header img
{
    width: 75%;
}

#intro
{
    float: left;
    margin: 100px;
    padding: 0;
}
#download1
{
    margin-top: 50px;
    float: left;
    width: 550px;
    height: auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    grid-gap: 10px;
    padding: 10px;
}

#d_box
{
    position: relative;
    color: white;   
    padding: 20px 40px 40px;
    margin: 15px;
    text-align: center;
    font-size: 20px;
    overflow: hidden;
    border-radius: 20px;
    
}
#d_box h3
{
    margin: 0;
    padding: 0;
    font-size: 40px;
    background: blue;
    border-radius: 20px;
}
#download1 #d_box:nth-child(1)
{
    background: linear-gradient(360deg,#086d35,#00ff72);
}

#footer
{
    width: auto;
    height: auto;
    background: purple;
    text-align: center;
    color: white;
    float: right;
    font-size: 12px;
}

/*contact us*/
#contact
{
    text-align: center;
}
#contact img
{
    margin: 5px;
    padding: 0;
}