<div class="container">
    <div class="sidebar"></div>
    <div class="content"></div>
</div>
.container {
    display: flex;
    height: 100vh;
}

.sidebar {
    width: 260px;
    background: #565656;
}

.content {
    background: #f1f1f1;
    width: calc(100% - 260px);
}
View Compiled

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.