body, html
{
    width: 100%;
    height: 100%;
}
.intro-section, .services-section
{
    height: 100%;
    padding-top: 150px;
    text-align: center;
    background: #fff;
}
.about-section, .contact-section
{
    height: 100%;
    padding-top: 150px;
    text-align: center;
    background: #eee;
}