CSS (or jQuery, for that matter) can’t animate between display: none;
and display: block;
. Worse yet: it can’t animate between height: 0
and height: auto
. So you need to hard code the height (if you can’t hard code the values then you need to use javascript, but this is an entirely different question);
#main-image{
height: 0;
overflow: hidden;
background: red;
-prefix-animation: slide 1s ease 3.5s forwards;
}
@-prefix-keyframes slide {
from {height: 0;}
to {height: 300px;}
}
You mention that you’re using Animate.css, which I’m not familiar with, so this is a vanilla CSS.
You can see a demo here: http://jsfiddle.net/duopixel/qD5XX/