#container {
    height: 500px;
    position: static; 
    width: 500px;
    background-color: gray;
}
#square1 {
    background-color: red;
    height: 100px;
    width: 100px;
     position:relative;
    top: 0;
    left: 40px; 
    /* position:absolute;
    top: 0;
    right: 0; */
}
#square2 {
     position: static; 
    background-color: blue;
    height: 100px;
    width: 100px;
     top: 0;
    left: 0; 
}
#square3 {
    background-color: green;
    height: 100px;
    width: 100px;
}
#square4 {
    background-color: black;
    height: 100px;
    width: 100px;
}

* {
    border: 1px solid red !important;
} 

div {
    margin: 0 auto;
    border: 5px solid black;
    padding: 2px;
} 

p {
    padding: 20px;
}

.inline {
    display: inline;
}

.block {
    display: block;
}

.inline-block {
    display: inline-block;
}