style.css

*, *:before, *:after{
    margin:0;
    padding:0;
    box-sizing: border-box;
}

body{
    background-color: #f2dfc4;
}

header{
    text-align: center;
    padding:20px;
    margin-bottom: 20px;
}

main{
    display:flex;
}



.addBook{
    padding:10px;
    padding-top: 0px;
    flex:1;
}

.myBooks *{
    margin:10px;
    
    
}

.input-div{     
    background-color: white;  
    border: 1px solid red;
    margin: 5px 10px 5px 10px;
    padding: 10px 10px 10px 5px;
    border: 1px solid #CCC;
    border-radius: 5px;
}
input[type=text],
input[type=number]{    
    margin:0px;
    padding:10px;
    width:100%;
    border:none;
    outline:none;
}
input[type=submit]{
    background-color:#8ad45f;
    outline: none;
    padding:10px 50px;
    border:1px solid #478a20;    
    border-radius: 5px;
    cursor: pointer;
    font-size: 1.2em;
    
}
input[type=submit]:hover{
    background-color: rgba(138, 212, 95,0.4);
}
.showBooks{
    align-self: flex-start;    
    flex:2;
    border-left: 2px solid #DBD0C0;
}
#myTable{
    width:100%;
    text-align: center;
}
#myTable *{
    padding:10px;
}

#myTable tr:nth-child(odd){
    background-color: #F9CF93;    
}
#myTable tr:nth-child(even){
    background-color:#FAEEE0;
}
    

#myTable #tableHeader{
    background-color: #DBD0C0;
}

.deleteButton{    
    background:#FF5C58;
    border: none;
    color: white;
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
    cursor: pointer;
    
}
.changeButton{    
    background:#79b2e8;
    border: none;
    color: white;
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
    cursor: pointer;
    
}

.invalid{
    border:1px solid red;
}
.error{
    color:red;
    display:none;
}