menu.css

.menu { 
    width: 150px; 
    background-color: #e6e6e6; 
    float: left; 
}

.menu ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
}

.menu ul li {
    float: left; /* This makes each list item float to the left */
    margin-right: 20px; /* Adds some space between the menu items */
}

.menu ul li a {
    display: block; /* Makes the entire area of the list item clickable */
    padding: 10px; /* Adds some padding for better appearance */
    text-decoration: none; /* Removes the underline from the links */
    color: #315eff; /* Set link color */
}

/* Clearfix to contain the floated elements */
.menu ul:after {
    content: "";
    display: table;
    clear: both;
}