#left-panel { height: 90%; overflow-y: auto; border-right: 1px solid #ccc; } #right-panel { height: 90%; overflow-y: auto; } #combine-button { position: absolute; bottom: 10px; left: 10px; width: calc(100% - 20px); background-color: orange; color: white; font-size: 16px; border-radius: 5px; border: none; padding: 10px; } #download-zip { position: absolute; bottom: 10px; right: 10px; width: calc(100% - 20px); background-color: blue; color: white; font-size: 16px; border-radius: 5px; border: none; padding: 10px; }