You should change class selector .konteineris
to ID selector #konteineris
:
#konteineris {
visibility:hidden;
}
and in html change <div class="konteineris">
to <div id="konteineris">
Or you need just change your JS to:
window.onload = function() {
document.getElementsByClassName("konteineris")[ 0 ].style.visibility = "display";
};
Also there is no display
value in visibility
CSS property. So should be:
window.onload = function() {
document.getElementsByClassName("konteineris")[ 0 ].style.visibility = "visible";
};