让网站的顶部菜单条导航栏跟随悬浮置顶显示，确保下滚翻页时菜单总是显示。
css代码
/* 仅桌面端固定顶部导航 */
@media (min-width: 769px) {
#masthead.site-header {
position: fixed !important;
top: 0 !important;
left: 0 !important;
right: 0 !important;
width: 100% !important;
z-index: 9998 !important;
background: #fff !important;
box-shadow: 0 2px 8px rgba(0,0,0,0.15) !important;
}
body {
padding-top: 70px !important;
}
}
