.row{
  margin: 0 -20px;
}

.one-half, .one-third, .two-third, .one-fourth{
  box-sizing: border-box; 
  float: left;
  min-height: 1px;
  padding-left: 20px;
  padding-right: 20px;
}

.one-half{
  width: 50%;
}

.one-third{
  width: 33.33%;
  text-align: center;
}

.two-third{
  width: 66.66%;
}

/*----920px----*/
@media only screen and (max-width: 920px){  
  #top{
    display: block;
    height: 100%;
    padding: 30px 0 100px 0;
  }
  
  #main-h1{
    font-size: 34px;
    line-height: 1.6;
    padding-top: 40px;
  }

  #main-h2{
    font-size: 28px;
    line-height: 1.6;
  }
  
  #top .button{
    margin-top: 10px;
  }
  
  #prolog{
    margin-bottom: 0;
    padding-bottom: 10px;
  }
  
  #collection{
    padding-top: 0;
  }
  
  .connect .one-third{
    width: 100%; 
    float: none;
  }
}

/*----775px----*/
@media only screen and (max-width: 775px){
  .one-half, .one-third, .two-third, .one-fourth{
    width: 100%; 
    float: none;
  }
  
  #top{
    background-position: top left;
  }
  
  #main-h1, #main-h2 {
    text-align: center;
    padding-left: 0;
  }
  
  #top .button{
    text-align: center;
    padding: 20px 0 0 0;
  }
    
  h1{
    font-size: 30px;
  }
  
  h3{
    font-size: 22px;
  }
  
  h5, p, li{
    text-align: left;
  }
  
  #main-menu ul li, #collection p, #course-list li, footer p, footer li{
    text-align: center;
  }
  
  p{
    font-size: 18px;
  }
  
  ul{
    font-size: 18px;
  }
  
  .button a{
    font-size: 14px;
  }
  
  #course-large img{
    float: none;
    width: 100%;
    margin: 0 auto;
  }
  
  #course-large h3{
    margin-top: 10px;
  }
  
  .illustration{
    width: 100%;
    float: none;   
}
  
  #portrait .center-box{
    max-width: 500px;
  }
  
  .teacher img{
    width: 75%;
  }
  
  #description .two-third h1{
    text-align: center;
  }
  
  #description .two-third h3{
    text-align: center;
  }
  
  #course-list .last{
  padding-bottom: 20px;
  border-bottom: 1.5px solid #8fb8c9;
}
  
  footer p{
    font-size: 14px;
  }
  
  footer ul{
    padding:0;
    margin-bottom: 20px;
}

  footer ul li{
    display: inherit;
    border: none;
    padding: 5px 0;
    font-size: 14px;
  }
}