/* styles.css */
body {
    font-family: Arial, sans-serif;
    text-align: center;
    /*background-color: #f0f0f0;*/
	background-color: #FFFFFF;
    margin: 0;
    padding: 20px;
}

h1 {
    color: #333;
}
h3 {
    /*color: #74F333;*/
	color: #0000FF
}
button {
    padding: 10px 20px;
    font-size: 16px;
    cursor: pointer;
}

#mensaje {
    margin-top: 20px;
    font-size: 18px;
    color: #007BFF;
}
<style>
    float-wa{
        position:fixed;
        width:60px;
        height:60px;
        bottom:40px;
        right:40px;
        background-color:#25d366;
        color:#FFF;
        border-radius:50px;
        text-align:center;
        font-size:30px;
        z-index:100;
    }
</style>