.all_body{
    margin-top: 20px;
    width: 90%;
    margin: 20px auto;
}

/* selectの装飾 */
#seminar_dropdown {
    padding: 5px; 
    margin-bottom: 20px;
    font-size: 16px;
    border: 2px solid #2c7acd;
    border-radius: 5px;
    background-color: #f8f9fa;
    color: #333;
    cursor: pointer;
    transition: all 0.3s ease;
}