.submenu {
  display: none;
  position: static;
  top: 100%;
  left: 0;
  min-width: 160px;
  box-shadow: 0 8px 16px 0 rgba(0,0,0,0.2);
  z-index: 1;
  opacity: 1;
  text-align: center; /* 使文本水平居中 */
}

.submenu li {
  display: block;
}

.submenu li a {
  padding: 10px 20px;
  font-size: 14px;
}

/* 当鼠标悬停在包含子菜单的项目上时，显示子菜单 */
.menu ul li:hover > .submenu {
  display: block;
}
.collapse:hover > .submenu {
  display: block;
}


/* .menu .nav-item {
  font-size: 18px; 
} */
/* #webmainmenu
{
margin-left: 20vw;

} */
#webmainimg{
margin-top: -15px;
}