How to make it so that when the page loads after 3 seconds, 1 block is hidden and another one appears?

Question

JavaScript

The second block is initially hidden.
Help me please.

Answer 1

learn Russian first
https://jsfiddle.net/S1ashka/ovzjpr85/

Answer 2

$(window).load(function() {
    $('.block1').delay(3000).hide(0); // или fadeOut(0)
    $('.block2').show(0); // или fadeIn(0)
});

Answer 3

Examples above or animation css.