.header {background-image: url("https://singularityhub.com/wp-content/uploads/2018/08/circuit-board-electronic-computer-hardware-technology_shutterstock_515152267.jpg"); padding: 20px;color:white; text-align:center;}
.column {float: left;width: 30%;padding: 15px;}
.row:after {content: "";display: table;clear: both;}
.topnav {position:sticky; top:10px;background-color:#3f98d4; overflow: hidden; justify-content:space-between;border-radius: 10px; opacity:90%}
.dropbtn {background-color: #3f98d4;color: white;display: inline-block;padding: 14px 26px;font-size: 16px; border: none;cursor: pointer;text-decoration: none;width: 29%;font-size:20px; opacity:90%; border: none;}
.dropbtn:hover {background-color: #ddd;color: black;opacity:90%}
.topnav.responsive a {float: none;display: block;text-align: left;}
.dropdown-content {
  display: none;
  position: sticky;
  top: 68px;
  background-color: #3f98d4;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  z-index: 1;
  width: 29%;
  border-radius: 10px;
}
.dropbtn:hover, .dropbtn:focus {
  background-color: #2980B9;
}
.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}
.dropdown-content a:hover {background-color: #ddd}
body {background-color:lightblue;}
h2 {color:red;}
.footer {position: fixed; left: 0px; bottom: 10px; width: 100%; background-color: #3f98d4; color: white; text-align: center; border-radius: 10px; Opacity:90%;}
.br {height: 10px;}
.show {display:block;}